I'm OLD school.  My first RPG ever was FF1 for the 8 bit nintendo.  My top 10 all time list (for all systems)

1) Lufia ( very underrated) 2) FF2 3) FF7 4) FFX 5) Legend Of Dragoon ( A GREAT game) 6) FF12/ Crono Trigger (tie)  7) Star Ocean for PS1 8) Dragon Warrior 7  9) FF3 10) FF1

Other really good ones include Dragon Quest 8, Star Ocean till the end of time, Breath of fire 1 and 2 (man did these games get worse and worse) FF8 and 9, Lufia 2.

As far as Dragon Quest vs. Star ocean..it depends on what your preference is.  You won;t go wrong with either one.  I liked Dragon Quest myself because it was really midieval and old school...sometimes less is more.  Its a little bit cartoonish, but it has a good story and decent side quests.  Star Ocean is a lot more futuristic...you'll probably need the strategy guide because its very complicated, especially all the item creation stuff.  Both are pretty much GUARANTEED enjoyment so you can;t go wrong.  I know its not PS2, but if you can get a hold of legend of Dragoon...thats a real dark horse that should please you.

PS: AWESOME thread, I was actually looking for somethign like this to get to know the RPG games for PS2 a little better.

I'm guessing I'm older than the average person on here, so a lot of people may not agree with me on this one but.......   For it's time, FF2 was incredible and in my opinion, the best one of the series.   They're all awesome, and all of them are must owns, but here's my rankings:

1) FF2 2) FF7 3) FFX  4) FF3  5) FF12  6) FF1 7) FF8 8) FF9