I love a challenge!
To me, the Xbox ranks high for a number of reasons:
1) Absolute ass kicking power, yes each latest and greatest system will push the evelope but to me the Xbox not only pushed it but threw it on the ground and stepped on it.
2) Hard drive, no real new technology here just the application of a tool available for years but virtualy ignored and scoffed at in the console realm. PC games have taken advantage of them forever but Microsoft was the first to step up to the plate. What are the chances that all of the next wave of consoles will have them? Pretty damn good.
3) Xbox Live, built in and supported broadband capabilities. True, during the Dreamcasts' brief run dial up was pretty much it and thus the experience was inherently limited. But neither Sony or Nintendo had the foresight, or guts, to build the capability into their systems. And Microsofts' online strategy is extremely strong. Add to that the ability to download new levles and items for games and it's just too big a benefit to ignore. I paid $50 for Splinter Cell, beat it, and then was able to download a new level for FREE. Same thing with MechAssault. My money goes further with this ability.
4) Truly usable system link (with the added bonus of the ethernet port), anyone that has ever played Halo using 4 Xboxs cannot argue this aspect. Time and time again I transported two 27 inch televisions, two Xboxs, two copies of Halo, and multiple controllers to Nicks' house so we could kill into the wee hours of the morning. No other console has gotten so many friends together at a time and they could all participate at once, even Matchstick.
5) Halo, FPS on consoles (with some Nintendo exceptions) have had their ups and downs and have mostly been slammed by PC gamers as not being flexible or deep enough. But Halo changed all that, I can't count the number of computer geek friends I have that would NEVER play console games but bought an Xbox so they could play Halo. And because of it's huge multiplayer abilities it's really two games in one. And it was a launch title.
6) Vision, the PS2 will go down in history as one of the most popular systems of all time (even though it kicked my Dreamcast to the curb), but just about a year into the PS2s life cycle Microsoft forced Sony into a poker game and the winner is all of us gamers. Xbox has a hard drive, Sony builds a peripheral hard drive. Xbox has broadband capability, Sony builds a broadband module. Sure Sony allowed for these capabilities with expansion ports but why not go ahead and give them to us right off the bat and free of charge. Now there is no argument about which system is the strongest at this time, the PS2 has a huge advantage in units sold and titles but Microsoft, in my opinion, has forced Sony and everyone else to redefine what console gaming is all about and has accelerated the development curve.
7) Total lack of fear, Microsoft sunk untold millions into this system and continues to do so and for the most part everything they have done has been to the benefit of the consumer. Did Sony drop their system price a year into it's life cycle, or include games for free (remember when every console came with a game and two controllers?). Nintendo has their outdated business practices that have caused many of their systems to be considered failures despite their capabilities. Sony waited to do things like lower system and game prices, and add additional capabilities until they were absolutely forced to (in my opinion).
At the time of its' release most people wrote off the Xbox as a clunky PC in consoles' clothing. But the system has thrived, just the buy in for Xbox Live shows what the potential is for this sytem. And every day it seems as if I get new news of increased benefits for me.
I bought the Xbox after having stepped away from gaming for about a year after the heartbreak that was the Dreamcast. When the Xbox came out I was reluctant to plunk down money on any system and really debated between it and the PS2. But after weighing the abilities of each I gambled (a bit) and went with the Xbox because I figured Microsoft was in it for the long haul. I have since bought a PS2 and a Gamecube and love them both. But in my mind I have already gotten a full generations worth of play and innovation out of my Xbox and they haven't really even scratched the surface of what they can do.
To me the system is important to the evolution of console gaming because it rewrote the definition of what a console should and can be. In relative comparison the PS2 and Gamecube have merely taken the next logical steps in power and little else. So if each generation of system has it's high water mark then to me the Xbox is currently it so it's overall contribution to gaming as a whole cannot be ignored.
And finally, any system that has a game like Halo that can cause adult (relatively) males well versed in everything from movies, to books, to music, to porn, to sit around for hours doing little else but dreaming up character names while ignoring everything around them has to be a winner.