Damn right! MGS2 does the whole "Xenosaga" thing better than XS, before XS ever did it! OoO Seriously though, I DO love MGS2. I've replayed the game endlessly. I think it's incredible fun, and I love its ludicrously over-the-top cinematics and fun, post-modern age (don't make me link to Tim Rogers, people). Hell, MGS1-3, really. I don't know how many people consider them to be RPGs, but I do; just not turn-based, but they share enough other things in common with the JRPG genre. Tactical Espionage Action/RPGs, w00t!

If you love the Xeno series' focus on awesome, thoroughly Japanese Mecha craziness, then I'd reccomend another game by Kojima Productions: Zone of the Enders: The 2nd Runner. ZOE2 is the best thing to ever have mechs, EVER, and is also the greatest action game of all time in my opinion. It's not an RPG, but if you have even the slightest love of mecha: BUY IT. It will change your life, and ruin other mech-related things for you.

I have found that a lot of fans of XS seem to enjoy the .hack// series, specifically the recent "G.U." trilogy that hit the PS2. I have all three, but haven't gotten around to them just yet.

Beyond those, you need to be looking at the "Shin Megami Tensei Renaissance" for the PS2. These are the RPGs that completely ruined XS for me, as they are infinitely more polished and well-written, but also cover similarly epic and unique moral/philosophical/religious ground. If you want a place to get started, I reccomend the just-released Persona 3: FES. It is THE definitive Persona 3 experience (being both a director's cut to the original P3 release, as well as a sequel to it), and is available for $30 new. Shin Megami Tensei: Nocturne and both Digital Devil Saga games are absolutely 10/10 brilliant, and they've recently experienced a re-print (my local game stores have multiple copies of each).

To anyone suggesting Xenogears: read the first post.

At any rate, those are the only games I can think of that are "similar" to XS. I really can't reccomend Shin Megami Tensei enough. For my money, they offer all of Xenosaga's strengths, they do away with the weaknesses, and are ultimately superior experiences that I will likely always cherish.