I feel your pain. In 15+ years I've yet to see a truly good game.
Quest for Glory series: semi-interesting story, mediocre gameplay. Meh.
Total Annihilation, Supreme Commander: Better economy model than all other strategy games, better implementation of warfare, but still meh overall. The actual gameplay is utterly tedious, and the battles aren't actually satisfying.
Die by the Sword: Imprecise, but playable implementation of physics-based swordplay. Gets boring after an hour or two though.
Hammerfight: Better physics, more solid and streamlined interface, but still only a few really interesting hours. Would have been amazing with multiplayer.
Dwarf Fortress: Interesting concept, but bland gameplay overall. May hold my attention if Toady codes true sentience in to the members of the game's races.
Minecraft: Same problem as DF - bland, but even less depth.
All Blizzard games: Again, just bland, with nothing to grab or hold attention. Not saying the games are poorly-made - the concepts are poor, not their execution.
My requirements for a legitimately good game would be:
Strategy(RTS or TBS): A.I. that is truly intelligent. Can out-think and surprise the people that coded it. Nothing pre-scripted. Learns within and across games. Reacts to macro and micro situations in ways that actual humans would. Can keep up with the exploded economy in the late-game, so that your horde of super-units is met by a bigger horde of super-units, as opposed to one (that specific example is from SupCom).
RPG/MMO/any game where you talk to dudes: NPCs whose speech is procedurally generated, and completely indistinguishable from human interaction, if there is social interaction with NPCs at all. Do it right, or don't do it. Don't be that guy. You know, Oblivion.
Any game with single-unit control (fighting games, platformers, etc.): Actual battles. Visceral. Emergent from the game's physics engine. None of this pre-coded "special move" bullshit. The physics engine should be fully accurate, such that any weapon or fighting style can be used, and it will behave predictably, according to how it functions in the real world. No health, no numerical damage. DF makes an admirable attempt at this, but text is just not the correct medium. Such a game would require an interface that can take inputs for all joints, and all ranges of motion simultaneously, as well as giving accurate feedback for inertia and material textures.