Well we can NOW, back when it was first released it ran horribly, and even playing it patched, with improved textures, on a much more powerful system, I STILL get this disconnect whenever I move around, interact with the environment, etc. It's hard to explain what I mean by that, but it just doesn't feel like I'm there; Alex just doesn't move right somehow, and every time a light switch disappears when you look at it from the wrong angle it keeps driving home the point that you're playing a game.
True story: When I first fired up the game I was convinced my sound was broken, because everyone sounded tinny and robotic, and I spent hours scouring forums trying to find the setting I needed to fix it's "rampant misconfiguration". Except all the voicework really IS that low grade, every single character sounds like an obvious recording! They spent so much time on the graphics (and didn't even get them playing properly on monstrous systems when it was released) and they release it with horribly compressed audio? Once again, every time anyone talked I was pulled right out of the experience because the sound was so bad. It wouldn't surprise me that they compressed the audio because the graphics were already pushing the poor X-Box too hard, giving me one more reason to hate the blasted contraption.
If I had never played the original, I would still contend that Invisible War wasn't a very good game. Having played the original, most of what I loved about it was cruelly stripped away, and all the good things they kept were dumbed down, ugly, soulless imitations of the original. There were some cool settings, some interesting plot twists, but they didn't overcome the overwhelmingly bad elements (everything else). I know empirically that the story wasn't bad, but it didn't have the same level of resonance with me partly because it tried to reconcile all the various endings from the original and threw them into a world that didn't feel like ours anymore.
So in short, yes Deus Ex 2 WAS as horrible as it was touted to be, it's just there are tons of even more horrible FPS games to compare it with. Just because something is better then a crappy game doesn't mean it's not a crappy game itself.
On a related note: Being the best FPS on a console is like winning the Special Olympics, so what's that say about the competition?