No Dark Sun for you, then? On a strict reading, Dragonlance is also out, as it doesn't have orcs. (I forgot whether or not it has kobolds.)In essence...
...
* Longswords and Plate-mail
...
* Goblins, Kobolds, Orcs, Undead and Giants
* Color-Coded, Elemental-Based Dragons
...
I realize scores of other games uses many if not all of these, but D&D stops being D&D when they lose these elements.
I don't know where the line in the sand is, but for me 4E has crossed it. There's a certain vibe and a required degree of suspension of disbelief in D&D worlds and rules which it lacks. I don't believe in the 4E milieu. The illusion is broken, and only a pumpkin and some white mice remain.
Not sure what systems you tried, but quite a few other RPGs have classes in all but name. If you meant classes and levels, OTOH, I can't think of many either.I'll go with classes, one of the big divides between dnd and every other system I've tried.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.