I have a wide selection of boardgames, some current favourites in my play group are as follows…
For more players: Battlestar Galactica or Rails of Europe.
For fewer players: Dominion, Race for the Galaxy, Tigris & Euphrates or Cave Troll.
For two players: Dominion, Race for the Galaxy, Battlelore, Memoir ’44, or War of the Ring
Personally I love large multiplayer conflicts, but finding players that can handle those is difficult (Warrior Knights, Twilight Imperium, Conquest of the Empire, Age of Conan, Starcraft and even Risk 2210 and others are all languishing on the shelves for want of players).
P.S. While I find Risk 2210 (not to be confused with basic Risk) to be imminently playable, I regrettably have to advise that Risk: Godstorm should be avoided for its random chaos and boring, overcrowded Underworld elements.