A bit late to the party, but here's my €0,02
First off, I need to establish that I am mostly a Scifi and Fantasy player with a strong emphasis on skirmish gaming; the big battles have grown out of fashion pretty much in my local scene.
* So, with that stated, for me, rules need to be simple and concise, yet granular enough to give enough variety between units.
A game that I think does this well: Grimdark Future (Firefight). A game that I think does not: Infinity.
* This also means I'm a big fan of opposed dice rolls with as few modifiers and ways of calculating as possible. A kind of bluffing system is also very fun.
A game that does this very well is Bushido. A game that I find is not so good at this: Infinity.
* Special rules are what often give flavour to games, but I absolutely abhor games that stack abilities, combo's and synergies between units to pull of some kind of miraculous effect that completely alters the whole game.
A game that I think does this well: Bushido. A game that I find failing horribly at this: Warmachine/Hordes.
* I like it when abilities are clearly stated on character cards, with easily trackable health, ammo/magic etc, and all special rules for that particular unit/miniature. Additional cards with equipment are also great, as are tokens to track the above. I'm less enthused by tracking health by striking off dots with whiteboard pens.
A game that I find does this very well: X-Wing. A game that obviously does not: Warhammer 40K 3rd to 6th edition (I haven't played any of the later ones).
* I like the option in a game to add an additional faction or encounter(s) to the game using a sturdy AI system.
A game that I find does this well: Frostgrave. A game that I find is not so good at this: The Drowned Earth.
* And obviously, a game needs to be fun; as someone stated in this thread before: it's a game, and games are supposed to be fun. What's the point of playing a game otherwise? It's not a job after all. (This reminds me of the very old starter box of the 'Oog des Meesters' roleplaying game, which boldly stated on the box lid 'Professional Edition', and I've always wondered just how many professional OdM players there actually were. And how one went about becoming one!

).
So yeah; these are all just my experiences, preferences and opinions: please take them for what they are...
