The Final Fantasy games are my weakness for this. I have FFX, X-2, XII and Revenant Wings, and Tactics Advance. Out of those, the only one I've beaten the final boss on is Tactics Advance. Revenant Wings, I made it to the final boss but keep failing, and can't finish all the sidequests as well (which I'm trying to do). TA, I beat but couldn't access the rest of the sidequests (so I'm playing through it again to do so). X and X-2, I've made it near the final bosses but was beaten by Braska's Final Aeon and the Magus Sisters, respectively. Never bothered getting every sidequest, though I will do when I next play X-2. As for XII, whenever I play it I make it partway through then hav to leave it for several months because I go off to university for another semester (the PS2 isn't mine, it's my family's, so when I go away the console stays at home - fortunately I have my own Xbox 360 for gaming away...). Furthest I've made in FF XII is Giruvegan, though I was pretty weak and hadn't bothered levelling up my guys much...
Anyway, right now I'm playing through X again, currently on Mount Gagazet, and after that I'll try and get 100% for the first time ever on X-2. I can always leave XII until later, hopefully I'll have XIII by then so I can play that at university...
EDIT: Oh, not to mention the current cam[paign I'm playing on Rome: Total War. Must be about 60 hours in or something, and I'm still only halfway
. 31 provinces captured so far, and ready to attack Rome, though I won't until I have a stronger force and have finished taking care of Pontus and Egypt... What a long game it is... 
Anyway, right now I'm playing through X again, currently on Mount Gagazet, and after that I'll try and get 100% for the first time ever on X-2. I can always leave XII until later, hopefully I'll have XIII by then so I can play that at university...
EDIT: Oh, not to mention the current cam[paign I'm playing on Rome: Total War. Must be about 60 hours in or something, and I'm still only halfway