Easy to answer Uncharted and Silent hill (the original).
I was musing the other day about Uncharted, when i saw the first e3 video of it way back before the PS3 launched. Looked at the trailer real and it looked so tediuous. All the cover based fire, dodgy gun play and platforming. Really wasnt impressed. SO Glad i downloaded the demo out because i was bored one afternoon... Uncharted is now my stand out favourite new franchise this generation.
And Silent Hill, back in the ps1 days, I was completely rote this off because i just took on glance and saw a blocky Resident Evil clone, without even the beautiful pre rendered backdrops that made that game so playable. a friend of a friend told me to play it, not to ask stupid questions, just do it, thank him later. So i rented it. And played it pretty much striaght through, ending up 2 3rds of the way through eventually putting the controller down at 4 in the morning. Hooked - went on to become one of my all time favourite games and likely my personal favourite franchise. so much so that neither SH:Homecoming, Nor Origins has ruined that....yet (lets see what damage downpour can do...)