With lots of games the genres get really specific so I am going to keep mine general so I don't have one game in categories like adventure/platformer or sandbox/rpg. I am also not going to list reasons for every single game. You only get two.
jrpgs: Legend of Dragoon(nothing will ever be better than this), Final Fantasy(older ones), and Lost Odyssey.
Legend of Dragoon, what more is there to say? Lots! It was huge and level design was awesome. It was innovative requiring precise timing, while at the same time not being impossible. The plot was pretty good, essential for an rpg. It is a classic.
RTS: Starcraft
Balanced! It was so perfectly balanced. Do you have any clue how hard it is to have such unique races without once being overly powerful?
N-N-Nuclear Launch detected, strongest move in the game, but ghosts were so easy to kill.
Holy Crap! Zergling rush...oh they die really easily.
Protoss is so efficient, its easy, and the units are of such fantastic quality! Oh they are so gosh darn expensive. Ugh, I have to learn to master these spells if I want to win.
Survival Horror: Resident Evil 4, Silent hills.
Adventure: Zelda's and only Mario 64