This question is getting hard for me, I've been gaming for over 20 years now. SMS, NES and MSDOS were my starting point. It also sometimes changes according to my mood. (but I love it at the same time hehe.)
1. Final Fantasy Tactics (I would say PSX, but I loved the new translation on PSP.)
2. Baldur's Gate II : Shadows of Amn (PC, no idea how many playthroughs of this I've played.)
3. Final Fantasy VI (Snes) (Though I'm willing to admit CT was the better game, by now I have feelings for FFVI lol.)
4. Earthbound (Snes) (Scratch and sniff game guide, hell yes! I still have fond memories of beating up hippies and Cranky Old Ladies.)
5. Castlevania : Symphony of the Night (PSX)
Many of the games some of you listed could've been here as well, but alas choices had to be made. I made a quick list of my faves from memory and then went by elimination. I guess the 90s were my "golden age" of gaming.
There's way too many honorable mentions, I could make a top 100. A few shoutouts : Lunar 1 & 2, Suikoden series, Xenogears, Vanguard Bandits, Dragon Warrior VII, Star Ocean 1 & 2, Tales series, The Legend of Heroes : Trails in the Sky, Ogre Battle, Tactics Ogre, Sierra Online's "Quest" games, Planescape Torment, Fallout 2, Arcanum, Daggerfall, Skyrim, Portal, God Hand, Vanquish, Chrono Trigger, Chrono Cross, Etrian Odyssey, SaGa Frontier, Super Mario Kart, Super Mario World, The Legend of Zelda : A Link to the Past, Phantasy Star IV, Shining Force, Valkyrie Profile, Radiata Stories, GTA San Andreas, Katamari Damacy, Shadow of the Colossus, SMT3 : Nocturne, GrimGrimoire, Final Fight, and I've got to stop myself now.