I'm probably in the minority here
Well, I'm in a good position to see at least a sliver of this world, working at a place that sells used video games as well as books. Not only do we get to see what folks are willing to sell (or even leave behind if we don't take!), but we field calls and questions for what they really want. Final Fantasy? Check. Pokemon games for Gameboy? Check, especially the Ruby and Sapphire versions. Even SNES games? Sure, if they're the right ones-- but we have boxes full of crap we can't even sell for two bucks, too.
Madden seems to be more of a social game than a "fun" game any more, at least if the resale market I've seen in any indication. The typical pattern is this: everyone wants the game for the first month or so, and we can't keep a copy on the shelf. Slowly, the game starts to pile up, and dropping the price doesn't make any difference, and eventually they're games we just turn down on sight. (Old basketball and baseball games follow a similar curve, if less pronounced.) Part of this is simple supply and demand- you can't sell someone a used game if they bought it new- but part of it, perhaps a majority, has to come down to quality, especially replay value. Apparently a majority of fans agree with you-- once the first impression has worn off, there's little in the game play to keep you around.
On a secondary note, while I agree that the mechanics of Civ2 were more fun, the lack of information, and really terrible AI, seriously dampened my nostalgia when I got sick of Civ3. As to Civ4 being overly complex . . I guess so. I think it gets easier once you get the general flow of the game down, but this can take at least a dozen games to reach if you didn't think about it too hard. But this complexity also helps the replay value, IMO, especially once I got the mechanics down enough to actually pull off a Cultural victory on purpose. (It made peace fun!) I can certainly see why someone wouldn't want to make that initial investment in time, though.
Ex ignorantia ad sapientiam; e luce ad tenebras