Does it count as being a "fan boy" if you are obsessed with playing the series, but you are still willing to admit its flaws and even point them out and openly criticize those games? IF so, then I have a good list:
Left 4 Dead - Full of bugs and glitches. Gameplay can get broken at times (especially during certain mutations). However I never stop having fun running through the streets and blowing people's brains out... I mean zombies. I'm totally not talking about real-life.
Pokemon - It'd be nice if we could do something difference once in a while other than badges, rivals, and elite four. Colosseum and XD Gale of Darkness shook the plot-up a bit (but sorta killed gameplay). Eventually, Pokemon will find the right balance, and Generation 5 is looking pretty good in those regards. The series is constantly making improvements and I love training for competitive play (whether I do competition or not).
Sonic - I LOVE the Sonic games. I prefer the 3D titles (SA, SA2, SHeroes, Unleashed, and bits of Shadow) but the series, as a whole, is pretty good. I get why people hate them. I even get frustrated with them. But I still have fun anyway.