Ok, before you bombard me with flames of terror, understand what I mean by this.....
Here is my take:
Because the XBOX can be modded, and because you can put a huge hard drive in it, and because you can put emulators of all the old classic systems on it, and MAME, and all the other stuff, I think that ultimately, years and years from now, the XBOX will be looked back upon as the most wonderfull video game system ever.
Not so much for what the XBOX can do, that Microsoft actually intended, but what it can do, as provided by all the hackers and coders and people out there that have been able to get the XBOX to do all these wonderful things.
Think about it. The XBOX can virutally be turned into a full blown media server for gamers! Name any other system that can play Atari 2600, NES, Genesis, Sega CD, Super Nintendo, TurboGrafx-16 and PC Engine virtually perfectly? Plus it can play MAME and Neo Geo and Game Boy Advance, etc, etc, etc,.
A modded XBOX, with a huge hard drive and all the emulators and roms loaded into it, is like a living breathing museum of the first 25 years of Video Game History.
You also have to think long term too. Think about in the future when 500 Gig hard drives will be super cheap. There will be a time, when somebody can put a freaking 500 gigabyte hard drive into a XBOX, with the right mod chip, and you could fill that 500 Gigs, with the entire freaking history of Video Games as we know it.
Of course, emulation of the Sega Saturn, Atari Jaguar and 3DO might never happen. And as powerfull as the XBOX is, it won't ever be able to emulate the Dreamcast or PS2 or GameCube.
But still.
Now, your take might be this...."Big deal, so the XBOX can emulate the classic old school systems, it's not like it's the first console to do that well (Dreamcast), nor will it likely be the last console to do that well".
Well, you may be right. But this will in all likelyhood be the ONLY console ever, to give you the freedom of being able to put everything onto a Hard Drive, and for things to be so freaking easy.
Mircosoft has learned their lessons from the original XBOX. With so many people modding their systems and putting huge hard drives in them, and loading them up with the latest Retail XBOX games, you will never, ever, see another system like this again.
Sony and Nintendo are very aware of what people are doing with their XBOXes, and they will undoubtably make sure that nothing of this sort happens with their next consoles.
Microsoft has already announced that the next XBOX won't have a "Hard Drive" as we know it.
I think 15 years from now, people will still be very interested in getting their hands on old XBOX systems, just because of all the crazy things that it can do, once it has been modded and turned out.