Playing time: 60-120 minutes
By: Bill Eberle, Jack Kittredge, Bill Norton, Peter Olotka, Kevin Wilson /  Mayfair Games [current] Fantasy Flight Games
Rank on BoardGameGeek:  1129th [current] 86th
One of the oldest games still on my shelf, Cosmic Encounter wasn't on its first edition when I got Mayfair's (it actually saw the light of day in 1977), and it would go through several more permutations before becoming the game it is now. My experience is with the 1991 version, but I'll do a little research so you know what you're getting into if you get it for yourself today.
Cosmic Encounter is a light strategy wargame of galactic expansion in which you play an alien people sending forces through a wormhole to establish bases on alien planets. Get a foothold on five planets across the galaxy (any players') and you win. You are limited by the random draw of the wormhole, the number of forces you can take with you, what alliances you might make and what rewards you can offer them, and the numbered cards and compromises you have in hand to "beat" your opponent. The twist: Each alien species (and there are dozens) has a unique "power" which manifests as a different way to cheat in the game. This might be anything from subverting alliances to having more powerful forces to bluffing about your card to turning enemy forces into your own... There are too many to list. And every time you play, the strategy completely changes based on the randomly selected aliens' dynamic.
Somehow, all starfaring aliens are based in a system that has 5 habitable planets, which are all habitable by other alien species. That's convenient (but see Components). Obviously, the only way to travel from system to system is the unreliable warp cone engine, which only rarely allows you to choose your target, though both parties' allies can get there easily enough once the wormhole is open. Dead troops go to the void, but their matter is eventually recycled into new troops. A lot of abstract notions, I'll agree, though I do like the fact you can drop compromises on the table instead of attack cards and get compensations, because of course some species stand to gain from allowing your bases on their territory. Where the theme shines is in the implementation of the alien powers. There's a lot of flavor there. Some of them are abstract, some seem more literal, but all of them are justified by a species' philosophy or physical characteristics, and that's a lot of fun.
My old Mayfair game isn't as pretty as the current edition, but I do like the interlocking systems, allow you to shape the "board" based on your actual number of players. And on the reverse side, one of my favorite things (sadly in black and white), different system types (one single Jovian planet, an asteroid field, binary suns, etc.) that give your aliens one more power and the game more flavor. The cards, cone, etc. are fine. What dates the game is the quality of the forces, simple round cardboard tokens of your particular color. Very plain. Now look at the current edition.
House Rules and Expansions
Mayfair also came out with More Cosmic Encounter, which I also own, restoring a lot of the Eon stuff to the game including Moons, Comets and Lucre (money), which make the game more complex and which some aliens might use. Having assembled a master deck of alien species, I only really use these additions if someone draws an alien that needs them. Having misread the rules back in college, I always played for Total Domination, i.e. the five planets your have to colonize had to be in the same system. That's why games ran so long. We also implemented Legacy-type rules so that any conquered species was out of the game, enslaved by the winner. If you ever drew that winning species and wanted to release a subjugated species, you could, a way to get your favorite back into the game, though at the risk of having to face off against it. (I remember Filth, Vampire and Zombie were debated several times.) Oh, and over the years, though I had PLENTY of aliens between the original box, More CE, and a Mayfair newsletter with fan-designed ones, I couldn't resist and added humans, Kryptonians and Daleks to the mix. Wrote about those HERE.
In conclusion: I love Cosmic Encounter to this day, played loads and loads of it but not lately, and am kind of sorry I don't suggest it more often when friends come over.