For an outdated game it still has features Madden still haven't been able to get right. You're on crack if you can't see 2K was helping push EA Sports. Madden would still be in the stone age if 2K wasn't around to push them.
We had online leagues in 2004. Madden just got them last year and it still wasn't as good as 2K5. Each League had their own Espn NFL website that tracked stats and you could post stories, Pics and everything.
EA took the idea of weekly prep in 2K5 and turned it into the NFL Head Coach games.
EA Copied the idea of 2K5's 25th Anniversary mode and put it in Madden 2009.
The cutting and juking they put in Madden 2009 was in 2K4 (2003). They pushed it more when they made T.O. the cover guy in 2K5.
Madden had stupid Madden cards when we had "The Crib".
We had custom soundtracks on the Xbox version. Where you could have certain music play during certain situations in the game. I believe Madden still doesn't do that trick.
Stuff like that has people going back to 2K5.