Runes.
Gems.
Runeword combinations.
Skill tree bonuses.
Synergies.
Crafting
etc.
more to it then that bub.
I don't really get how a game being dated = you can no longer min/max in it or something. You seem to not like old games which is kind of sad, who cares if the graphics suck or whatever. The games you play now already look like shit I guarantee it a month down the road. Guild Wars especially is already dated and looks pretty bad (and also has no min/maxing aspects at all, so bad example.). I don't see how I or anyone else (read: millions of people) who do this are ruining it for ourselves since we obviously still play the game after all these years for hours and hours and enjoy it? It is still an aspect of the game you are missing out on, even just the basic parts of it.
on the subject of D3 they've said they don't have a final # of classes so the FAQ is wrong, but tbh I expect 5. Barb, Doctor, a sorc like class, a long range like class, and a rogue like class imho.
I never said I don't like old games, I just find when it comes to old games you have to have played them when they originally came out, or at least a while ago. And even then, you can usually find newer and better games. Wait a minute, how can you even say it seems like I don't like old games? Did you not notice the entire fallout theme going on? That's a game I'd rather play than D2 when it comes to min/maxing (but you could argue it's not online but whatever I don't care right now).
It also seems like half the things you mentioned have to do with socketing items, once again, related to items. Is what I'm saying is that there are different ways to play a game. Diablo II is outdated, and the only reason why I'm playing it is because I want a dungeon crawler that I can play with my friends. The reason why YOU play it is because it's a game that you played back in the day, that has grown onto you, a game that you like to customize and blah blah blah. That's the way you (and lots others like to play). But not me and my friends. Are we missing out? No. We're just playing the way we want to play.
edit:
I thought of a semi-decent example. Ever played Gunz the duel? 3rd person shooter. Well in that game you can play normally, or you can learn a bunch of glitches and play k-style (ugh) which greatly increases your playing ability. K-style took a lot of skill to be able to do fully though. People who play k-style are playing the metagame I guess, where as non users are just playing normally. Nothing wrong with either.