My favorite game of all time has always been Chrono Trigger. It was the first non platformer that I had ever played, and the combination of storyline, replay value, and social awareness all made it one of the most important video games to have been made.
Most people are not akin to going and playing some of the older games, but I must say that if one has never gotten the opportunity to play Chrono Trigger, and one is an avid RPG fan, this is a game that must be played. It was one of the earlier games to bring in: multiple character switching, avoidable battle sequences, a good sound track, interesting storyline and character development( as all of the characters receive their own back story within the game), and a storyline which is socially relevant to the real world.
I love games of all types, save for most sports games. The first Zelda as well as A Link to the Past were wonderful. Final Fantasy Tactics and FF9 are the most underrated FF games in my opinion. Chrono Trigger is, however, my favorite game, and I believe it will forever hold that title.