Recs.
Updated
Cosmic Encounter is a sci-fi board game. Each player assumes the role as leader of an alien race. There are dozens of races, and each has its own unique powers.
The object of the game is to establish colonies in all the other players' planetary systems. Players take turns going on offense. During your offense, you will draw a "destiny card" which lets you know what your target planet is and who your opponent will be that round. Each player in the encounter fights for control of the planet by playing special cards and calling upon allies.
The first player who establishes 5 colonies outside of their home system is declared the winner.
SpecsUpdate
Pros
Pro Every game is unique
The basic rules of the game are background noise. The alien powers, both individually and as they interact with each other, determine the dynamic of each game you play, and each dynamic is radically different. For example, you can try different races and alien powers each time you play, and the way to mix and match them is almost limitless. This makes every game feel different than the one before it.
Pro The social component of the game requires you to strategize with other players
It's almost impossible to win on your own. When attacking or defending, you will get the chance to ask for allies on your turn, or assist others when they are engaged. Allies can help you win the attack or defense, but they will also gain benefits if successful. It is a team-based game, although each player is out for themselves in the end.
One of the neatest parts of the game are the negotiate cards - instead of laying down an attack card you can try to negotiate. If you both play negotiate cards, you have 1 minute to come to an agreement which can include creating new colonies, trading cards, or virtually anything. If the players don't come to agreeable terms within a minute, they both suffer a hefty penalty (4 of their ships are sent to the warp).
Pro Potential for very satisfying, creative plays
With so many unique combinations of alien powers and the fact you can form unstable alliances with other players, there's so many ways to get creative. For example, knowing when and where to pick your battles. Perhaps two other players just had an epic battle and now they're down a few ships - it would be the perfect time to swoop in and try to colonize their planets when they're weakened. Perhaps you have a special power that will give you an edge in a certain fight against another player. By paying attention to what's going on around you at all times, skillful tacticians will find all kinds of extremely clever or amusing plays to be possible.
Pro You have some influence over the theme of each game
At the beginning of each game, players are given 3-4 alien powers to choose from, usually taken at random. However, if you were trying to put together a specific theme - for example, a war between certain aliens races, or a battle using only certain powers - you can manually select the set of powers available to each player. This allows you to generate personalized games that have specific story to them or heavily revolve around a particular strategy or resource.
Pro Excellent expansions
There are six expansions which not only add a minimum of 20 new alien races with new powers each, but they also brings unique gameplay mechanics to the table. For example, Cosmic Conflict adds space quake hazards, and Cosmic Alliance adds new rules for teams and expands the game to 7 players.
Pro Not as complicated as it might sound
After you play one or two games, the basic mechanics become trivial to work with. Additionally, you only have to worry about learning as many alien powers as you have players in the game, so your personal knowledge and experience with the powers can grow slowly over time. Most alien powers take a minute or two to really understand, then the fun begins of finding creative or unique ways to develop strategies around them.
Cons
Con Can cause arguments
Due to the nature of the game, which has you working with others and then turning against them in the same breath, it can create some situations where people are going to feel used or mistreated. This can result in a lot of fighting or arguments, especially when playing with easily offended people.
Con Some alien powers are difficult to parse
Some of the cards have walls of text that look intimidating at first, and may take a slow read and group discussion to really figure out. Thankfully, the alien powers are divided into three sets based on "difficulty" which translates roughly to "difficulty to understand, and how much it disrupts basic gameplay." Green (easy) cards are usually simple enough that a child of 12 or so can understand them.