Threadjack time. The titles says "Favorite Bad Games" but you asked about RPGs. I'm ignoring the request and going with bad games in general, because RPGs that I like I usually think of them as authentically good. (Perhaps disliked by others, or lopsided in its virtue / flaws where I'm willing to focus on the good parts while ignoring the bad, but either way it's good to me.) Instead, the realm of "objectively bad games that I find myself still playing anyway" are usually strategy games. Playing Civ4 or Civ5 on the hard difficulty levels is, well, hard! Sometimes I want a break and to just win, and win big. I kinda liked knowing the perfect strategy in games like Civ2 or SMAC and rolling the AI on the toughest difficulty level. But those don't count because those are excellent games. And I played a bunch of MOO2 as well, and it's a severely flawed game (balance? what's that? how'd you like to do some more micromanagement?), but it's still a good game, so it doesn't count either.
The two strategy games I'd call bad that I've still sunk too much time into are:
A) Liberty or Death. Old SNES Koei game. Can only be played sanely either playing both sides and just role-playing around and attempting to have both sides use real strategies, or on an emulator as the British. (Okay, or as the US on the console, sure.) Why the difference? Because the game is BRUTALLY rigged in favor of the colonists. Massively. Hugely. They run around collecting huge taxes with their loyal militias guarding the entire map, while the British force runs on a shoestring and has all incompetent commanders. And crucially, just way fewer of them. And of course the Loyalists are Special, in the sense of they ride the special carriage to school and probably lose in fights with angry rabbits. The one thing the British have going for them is a better starting navy, which is good, because the AI is totally incompetent about avoiding the giant naval cannons pointed at their armies, and will cheerfully stand under their withering fire for no gain and lose all their troops. (But don't worry, Americans, with your excellent and efficient tax collection from a loving populace, you'll eventually be able afford a fine navy to tangle with the British.)
Anyway, you can be a genius in the actual battles, but the British are just massively screwed for a lot of reasons. Let's start with the most obvious one: in order to win the game, they need to conquer the MAP. Wipe the rebels out and clear them away. The problem? The map is pretty large, and you just don't have enough troops to do it with. There are like 72 provinces, and the British get maybe 90 officers total over the game - and start out with far less than that. And some of your officers, and especially the Loyalists, will likely get captured early. And as you force the Americans back, there's no conception that losing territory means less manpower or anything - the only effect is less funds (but the Americans are awash in funds anyway, from their huge territorial spread thanks to the militia tax collectors). So as the British spread their army more thinly and thinly and have just a tiny force at the front, the Americans are compressed and have hordes of troops where they want 'em. Doesn't matter we're in frigging' Ft. Stanwix, the extreme boonies where like 3,000 people at most lived - it can, and has been, the US recruiting center for some giant push back, almost like Ogre Battle or something where the periphery of the empire somehow launches a massive renewed rebellion. Yeah there are like 3,000 SOLDIERS coming at you from it.
Okay, so you're thinking that this is just a game about capturing officers then so as to reduce the number of regiments the Americans can throw at you. Yes and no. The problem is there is no "execute" button; you must imprison captured officers. And they never die of old age or prison riots or anything. And there are PRISON BREAKS. Yes, if you capture "too many" enemy officers, they start breaking out of prison and raising new armies to attack you with (shouldn't we just imprison them IN BRITAIN?!). Now, for the Americans, this isn't a big deal - since they have far more officers total than the British, if they've gotten to the point that British officers are escaping, that means there are few British left to fight. But for the British, it's a terrible problem, and means you should throw as many fish back as you can. Militia officers for sure - you "just" occupy the entire state, and the militia can't respawn in hostile territory to them. But you have to let the weaker officers go free too, so that you can be more assured that the badasses you capture stay in prison. Note also that this means that, perversely, Hard mode can be easier if you want to actually win the game - the one way for officers to die is via chance in battle. The odds of this go up, for both sides, on Normal or Hard mode.
To go back to the stats issue, officer stats plays a pretty huge role in how well your army performs. The Japanese seem convinced that every single Continental army officer was a super tactical badass, and the British were (almost) all morons. Maaaaaybe, but if we're playing to stereotype, they at least could have preserved the "Americans are undisciplined yokels" and "the British troops are at least properly drilled." But no! Plenty of British officers have terrible Discipline ratings and have lazy soldiers who can't do anything, and plenty of US officers other than von Steuben or Washington have high Discipline which makes it easy for them to have crack troops if they bother to spend time drilling. So perversely as the British you want to incent the attack-happy AI to attack you right away when they get new troops in, so you can kill 'em before the AI bothers to train 'em.
So. Why do I like this game? Because I want to play a simulation of the Revolutionary War, damnit. And the game does give you wildly historically inaccurate battles where your 1750 troops somehow defeat an unrushing mass of like 3000 American troops in a mega-slaughter that ends with 70% casualties on both sides, casualties that get replenished nearly for free after a mere 2-3 months. (Protip: The actual revolution's battles were much smaller, and had like 2-3% death rates if that.) And the music is shockingly not bad, if too repetitive.
B) Imperialism II. Build stuff which allows you to get more stuff which allows you to build an army which allows you to take Indian stuff which allows you to get even MORE stuff which enables you to get more ships & armies which enables you to kill even MORE Indians which enables you to get more stuff which enables you to attack harmless European minor countries you've been in a quiet no-shots-fired bizarro war with for 150 years, but now it's on, which enables you to eventually overthrow other major European powers and steal their colonies and steal their land and win. The history is just so bad in this game. And so is the economics - your fancy shmancy hard-working intelligentsia need HATS from the New World, specifically hats made from squirrels in the arctic or something, and if they don't get it they're not working, so having your colonies cut off means you spiral into despair and loss very fast. The diplomacy system is awful - you can't coordinate with an ally at all, so if 2 allies fight the same enemy, the only way to stop the war is for one to break the alliance and sign a separate peace. There's no way for both to come to peace at the same time (short of the unlikely event of the total defeat of one country). The retreat system is awful and far too forgiving - if there's a territory nearby that's unoccupied, you can always instantly retreat for free. It doesn't matter that your peasant levy is beign chased down by 5 regiments of horsemen, they GET AWAY and can "retreat to victory" and conquer into your homeland and other such nonsense. This MIGHT be okay if maintaining a large army was easy, but armies & ships inexplicably consume huge amounts of food (yes, food is the limiting factor for your army usually by lategame...), so you're stuck seeing where the enemy attacked, reloading a turn ago, then teleporting there to actually defend it lest someone break in.
Meanwhile, it turns out the entire New World was explored & exploited by like 1620 or so. Wut. Also there's absolutely 0 point in being nice to the Indians; if you pay the Indians large amounts of money, and research technologies, and build special units, you can gain the right to "buy" their land and then develop it and then they'll "sell" the goods to you cheap. Of course if you get into a war, the other European power will just murder the Indians and take the territory, rendering your investment worthless. OR you can just murder the Indians yourself, get XP for your troops, maybe build up to a general, and rather than "buy" the goods at a discount, get them for the price of 0$. And let you build things like forts in the province so it MIGHT hold against a European power (if you do the annoying reloading mentioned above.)
Lastly, the difficulty modes need work, like many old strategy games. On the hardest difficulty, you probably lose early, but if you somehow survive, you win as usual becuase the amount of cheating doesn't scale, and a human in the lategame should win. Sigh.
Why do I like Imp2? I dunno. See the first statement. It IS fun to build out your transportation network, and watch as resources cycle into each other and turn into stuff that you use to get more resources, repeat.