I would be inclined to say yes, but if it's really just some RPGs you are after, I may be more inclined to say no if your game collection is accurate. You've definitely missed out on a lot of gems for the PS2, like Persona 3 FES and Persona 4, both of which are relatively recent PS2 releases that can easily take you 70+ hours each. Going even further back into the PS2's lifespan you have games like Suikoden III and V, Dragon Quest VIII, Kingdom Hearts and so on. All good games that should give you hours upon hours of great playtime. And then on the PS3, there's Valkyria Chronicles and Disgaea 3, two really good and really deep SRPGs that I would definitely recommend.
If you are a huge fan of Western RPGs, though, a 360 will probably still be an excellent choice and may be more apt. Fable 2, Mass Effect, Mass Effect 2 in the near future, are all great WRPGs and definitely worthy of a purchase for somebody that doesn't outright loathe the WRPG genre. Otherwise, I really don't think the jRPGs on the 360 really justify a purchase over jRPGs on the PS2 you have yet to experience. Lost Odyssey is generally given high praise (even though I hated it), as is Vesperia, but there's a good chance the US will get the enhanced PS3 version of Vesperia so you probably wouldn't be missing out on that anyways. So in the end, it's probably just Lost Odyssey, Blue Dragon, Last Remnant, Infinite Undiscovery, Star Ocean and maybe a few other jRPGs that are released in the future. It's a decent size list of jRPGs, but LO is probably regarded the best of that bunch and the rest are mediocre (though there will be some who claim such and such game is too awesome for words and anybody who hates that game is a moron). The PS3's jRPG list pales in comparison because I don't even think it has one, but there are plenty of good games you can get for relatively cheap on the PS2 that I would probably get before getting a 360 if I was only getting the 360 for the jRPGs.
Just my opinion, but whatever way you go you probably won't be making a bad decision. Unless you spend that money on a pizza at Pizza Hut.