5) Kingdom Hearts (PS2) - When Disney and Square Enix decided to make a game, I thought it was a ridiculous concept that would fall flat. Little did they know that the product would actually be a good game, in fact one of the most fun RPGs I've played to this day. A mixture of a great battle system, excellent control, enjoyable accompanying music, minigames aplenty, and a plot that really drew me in, Kingdom Hearts was a game I just wanted to play and play more.
4) Ys VI: The Ark of Napishtim (PS2) - Most people wouldn't put this game in their top 5, but I'm going for most fun I've had with an RPG, and this game is high on my list. Ys has a GREAT control scheme, probably the best I've ever experienced in an action RPG. Add to that an excellent series of bosses, well-designed stages, and a kickin' soundtrack, and I just wanted to keep playing to beat the snot out of more enemies and beat bosses that would kill me over and over.
3) Final Fantasy XII (PS2) - I know why MMOs are so addictive, and FF XII was my teacher. It allowed me to experience a lot of what makes MMORPGs so appealing, while letting me escape having to pay a monthly fee. The gambit system, the myriad quests and hunts, and all my favorite critters from Ivalice all go into making this game amazingly fun and entertaining.
2) Shin Megami Tensei III: Nocturne (PS2) - I never played Pokemon, but SMT III is the next best thing, I figure. Collecting demons, raising their levels, and then fusing them into more powerful demons, all while traveling through a post-apocalyptic Tokyo to discover the reason the world ended and you didn't made this title incredibly engaging. What could be better... ?
1) Shin Megami Tensei: Persona 4 (PS2) - ... how about combining that with a well-done dating sim? I made myself not choose two games in the same series, and of the two, Persona 4, more so than Persona 3 FES, came out on top. Persona 4 is an improvement in every way on Persona 3 FES, with more developed social links, jobs to do, more stats, and just more options in general. I have had so much fun with this game, and I'm only halfway through it at the time of writing this. There is great voice acting, too, which puts it on top of 3 in terms of my favorite games of all time, and that's no easy job. So even though we are well into the next generation, this last generation title is probably my favorite of all of them.