@ DrSpock: 5 MB?
Heck there have been some earlier classics (which are still played today on mobile phones and whatnot, if those would be counted in a regular way by number of users they might very well be the most successful games ever made if perhaps not commercially.) which weren't bigger than 5 KByte and still! play nicely today... (though most of the more complicated of those games back then quite suffered from interface issues which made them hard to play. And the vast majority is just simple in the extreme. Not detracting from their fun gameplay though) and plenty of games in the 3-digit KByte range which can be described as nothing less than great classics. No need to get out the MB baton for that argument.
But give developers memory... (still one can't deny some hefty improvements in smooth gameplay and improved interface + non-eye-destroying visuals though...)
I remember Dynablaster's 1,5 MB to Bomberman's 50 MB (or later 100+MB?) and its still basically the same game... (oh and Dynablaster had an extensive single-player-mode + a basic but fun multiplayer one.
Bomberman just had extended multiplayer... Talking of dumbing down...)
Both not the best games or greatest classics but its very telling...
And the most beautiful thing about small games and less resources is that devs needed to be much less "wasteful" + possibilities for errors / oversights was much lower leading to polished games even without much extra-time spent in testing and tweaking.
If the real classics are played today (and i mean games which don't suffer badly from having those old graphics. Things like tetris + clones, elite + various spinnoffs, civ + various followups.) it proves that graphics alone just don't help in making a game good (because a lot of them still play out in a great way. At least if their graphics are not totally eye-destroying and the interface doesn't make the game unplayable.) and that lack of those needn't make a game bad + that the mind is quite capable of imagining things without the game depicting anything for it.
Its all down to gameplay / fun in the end. (and the size of some of those games (in game) is just mind-boggling (compared to the space they take on a hard-drive.) Say: Elite... Bigger gameworld than many of its offspring. Which literally are sometimes millions!
of times bigger in terms of drive-space needed.)
The most important improvements though have been in the areas of multiplayer and quite lately casual-gaming / party gaming.
One can complain about OOs and the likes all day but serial cable has been a disease as have dial-up modems and Internet-play without things like game-finding apps (like gamespy, battlenet and the likes.).
And one can't deny the success and necessity of multiplayer / casual + that they would not really have been possible in the old times to that extent.
If only the quality of the the old games could have been preserved.
(and some of them needn't have been lost in the process which makes it even sadder. This part is especially true for Civ4:Col if it wouldn't have been rushed all that hard and unfinished to fit the EtoA. Which makes the whole thing more or less impossible anyways...)
As special note goes to modding which might have been possible back then, but the scope has been taken to a whole new level in comparison due to the possibilities of the net. (That requires a company/publisher which allows it though (unless you want to stray to darker paths...). But Firaxis / Take 2 and a few others are decent in that regard.)
Sadly really outstanding AI (which work out in a fun way. Not those unbeatable cess-AIs) is still rather hard to come by.
But difficulty-levels and handicaps are at least some kind of adequate compensation for that and the reasons are understandable...