If I have to say a franchise that has been perfect for me, then that'd be Professor Layton. I'd loved all of its games so far, and I'm sure I'll love its lovechild with Phoenix Wright.
But if I have to say something that's gone for a long while, taking the good with the bad. Then... woah I can't decide. Everything has just gone to hell at some point. I guess Mario then. What do you know? Mario is my favorite game franchise of all time. Huh.
Edit: Oh yeah, funny that my nickname is Megaman themed, and yet it didn't even cross my mind when pondering. That's a sad reflection of some things nowadays. But I'm happy there are still really good games being made. (So I'm not saying gaming is doomed or anything like that.)
Official Rainierman of..! ... eh... Gamefaqs I guess...
Debated this in my head a long time... the most frustrating example was Final Fantasy which has 2 of my favorite games of all time (FF6, FF7) but also has some truly bad games out now. Gotta take the series as a whole, I think.
#1 - Civilization. When these games come out I own then within 24 hours, and within 48 hours... I've played them for 24 hours.
#2 - Fallout. Really, every game has been very good, and FO1/2 are classics.
#3 - Baldur's Gate. Only 2 (and a half) games in the series, but they are just that good.
"Life is like a box of chocolates. Diabetics can't enjoy either."