It took me forever to beat OoT because every time I made it to the Shadow Temple/Bottom of the Well, I stopped playing for like a month. And then I'd pick up the game and be like, "I don't know where I am or what I'm doing. TIME TO START OVER!" This went on for years before I finally finished Ocarina of Time.
I never finished Mario 64 but I've always had files that are 100% complete on it (thanks whoever owned it first). I wanna say I've had it for at least 8 years.
I've had FF12 for over 2 years (or was it 3?) now and last time I played it like a year ago or something I died to the final boss and I was like "oh" and haven't touched it since.
Honestly I can't think any specific examples, maybe Sonic the Hedgehog 3 and Knuckles? Yeah the ''complete" game.
Or maybe Earthbound, it took me a long time to beat it.
I think it took me about two and half years to fully complete Project X Zone.
It took me one year to actually beat it, and another year and a half for completion. Long game is loooong, repetitious (most of the chapters were rout missions, if I recall correctly) and filled to the brim with enemies. No plans on playing this title any time soon.
I think Dark Cloud was my longest to complete main game. Would have a lot of sporadic play sessions with it, but would find it a bit tedious after a while and have to put it down.