Final Fantasy - I actually used to take the piss out of it quite a bit, until I played my step-brother's copy of FFVII. I was hooked within minutes.
Persona - I played Persona 3 for a bit and it never really felt appealing. Decided to buy Persona 4 Golden and was blown away by it.
The Elder Scrolls (Skyrim) - I played Oblivion and absolutely hated it. Just a month after launch, Skyrim was going for half price so I decided to give it a try. I put 8 hours into it on the first day.