1) Twilight Imperium - it's long, pretty clunky, and the victory conditions are horribly disjointed. And it's pretty badly imbalanced - not just because of the random mapboard but also because the races range from really good to really bad. But the pieces are pretty and there really aren't any other space conquest games out there with fucking Death Stars. With a bit of streamlining and quicker playtime this would be a classic.
2) Battlelore/C&C - it's honestly a beginner's war game and nothing more. It's hard to even consider it a historical game because it's so heavily abstracted (in C&C's case). The special dice are unnecessary. And both Battlelore and C&C have confusing pieces that slows down setup. That being said the system is simple and fast to get into. Memoir '44 is the best variant - the German/Allied pieces are very distinct and there are only minor system tweaks. Not bad overall, but for an experienced gamer it's quite sucky.
3) Android - Suffers from bad marketing. It's supposed to be a murder-mystery turned "frame a suspect" with "conspiracy theory" and "journey of self-discovery" thrown in. Terribly disjointed flavor. I hated it. Especially because it had the fiddliest movement mechanic ever.
4) Arkham Horror - Best simulation of an RPG in one sitting. Can get very fiddly but otherwise hugely fun. Unlike Android, all your objectives are related. Pretty imbalanced characters though, and the expansions are dizzying.
5) Battlestar Galactica - No game simulates is source material so well. This is the Batman: Arkham Asylum of Boardgames. The key is the fantastic "traitor" mechanic coupled with a battlemap that exactly captures the feel of the series. The expansion is a bit disjointed, but even its disjointment mirrors how batshit insane most of the characters became in Season 3.
6) Chaos in the Old World - the game is honestly Acquire with some combat retooled for the Warhammer world. Yet it works. Fantastically. The Gods play like they should in fluff, and it's a fast simple 2 hour game to get into. So far my game group hasn't detected major imbalances either. The only downside is that it must really be played with 4 people.
7) Game of Thrones - A pretty good Diplomacy variant. The mechanics are well streamlined and the playing pieces are good. I liked it.
8) War of the Ring - Okay, I lied. This game also simulates its source material like no other, but "good vs evil" is kinda easier than "paranoid space survival". The brillance of this game is that it combines a Risk-style war game (Gondor & Rohan & others vs the Armies of Sauron), with a hide-and-seek style adventure (featuring the Fellowship). Plus, it has a gorgeous Collector's Edition.
9) Doom - Despite people groaning upon seeing the box, it actually played well. It actually felt a lot like Space Hulk. The main thing going against it is the fact that your dudes respawn when they die (like in the video game) which feels kinda weird in a boardgame, and the setup is painful. The wacky dice, personally speaking, actually work well for this game.
10) Descent - A lot like Doom, but more close range hack and slash. Suffers from many of the same problems as Doom. While Doom is mediocre bordering on good... Descent tends to be mediocre bordering on bad for me. Largely due to a lot of fiddly new rules on top of the Doom engine.
11) Age of Conan - The pieces are pretty. The main game itself is an okay Empire-building game with Risk elements. But Conan himself is limited to being an NPC who runs around and kills random stuff. Disappointing, but not a bad game per se.
12) Starcraft - Fiddly as hell (especially combat), long play time, and imbalances due to the maps make it a little hard to recommend. But the pieces are nice, the order system is interesting, and the three race interaction is preserved. With a bit more polish this would have been great.
13) Runewars - I was honestly tempted to dismiss this game as it has a similar combat resolution mechanic as Starcraft (fiddly cards! Why not dice?!) but the game won me over. It's basically what the Starcraft boardgame should have been... albeit this one is set in a fantasy setting.
14) Ad Astra - Settlers of Catan in space. With less annoying trading. Fantastic game!
And now I tire and will rest
