Megaman was always sorta iffy at best. Cool concept, good level/boss design, but the overall idea really just didnt work. Whole appeal was defeating bosses and snatching their cool weapons, but... watch basically anyone play any of the Megaman games (aside from maybe 9) and everyone just uses the basic Buster gun pretty much all the time even when they have other weapons, because the other weapons tended to not be very well designed. Unless they're playing 2, at which point they'll defeat Metal Man and proceed to use the Metal Blades for the rest of the game. Usually the boss weapons are only used VS other bosses, which has a tendency to make them trivial fights, thus wasting the otherwise good boss designs...
I like the first 3 games well enough but just sorta lost interest after that.
As for stuff I personally never could really get into...
Well, name a first person shooter that isnt freaking old, and chances are, I think it's bloody boring. I mean, really. Everything has to be "iron sights", hiding behind cover, and auto-regen in every bloody game. Whatever happened to running around like a maniac with a chaingun while dodging a bazillion fireballs? Oh, that's Too Hard, probably is why, feh. Doom-era games (as in, DOS Doom, not the recent one) I'm good with, but later stuff is just bleh.
So yeah, games like Halo or Call of Shooty Guy or whatever. They're just so freaking boring to me.
Also, pretty much any of Capcom's own fighting games. I've played so many fighting games (that arent made by Capcom). And I got good at them. REALLY good. And had such fun indeed. But give me one of Capcom's fighters... and I will tire of it really fast. It's hard to even describe why, without rambling for 3 pages in such a way that only a long-time gamer would even understand what I'm saying.
Dont get me wrong, I've tried them. I really have. Street Fighter, Marvel VS Capcom, whatever, I've given them all multiple chances, and... bleh. I just lose interest so fast.
And then the big one for me, FREAKING NETHACK. Yeah, I expect hardly anyone here to even know what that is. But as a longtime fan of Roguelikes, well, that's sort of THE game that any fan of the genre is expected to like. But I hate it. I *HATE* it. It honestly wins my award for "worst game I've ever seen". I've been gaming since the Atari 2600 days and I have nothing but free time, all the time, so a game hitting that level is one heck of a feat.
I've given it many chances. I've tried my best to figure out why in the numerous hells anyone likes it. Every single time I decide to put myself through that, I come away just feeling like my loathing of it is validated.
And I just. Dont. Get it.
And finally, most AAA games. Just... bleh. That's a whole other rant though, really.
So yeah, that's some of my "I couldnt ever get into these" entries. There are certainly others.