Me and Mrs A. have got a fair few - didn't think Mrs A. would be in to them but was pleasantly surprised!
Munchkin. Better with more than two players but can work with two. Plenty of replayability with the expansions you can get.
Carcassonne. 2-7 players. Works with two and again plenty of replay ability. Carcassonne Big Box will give you all the expansions at a lower price. Further expansions available.
Dominion. As always, better with more players, but two works well. Plenty of expansions which gives HUGE replayability due to amount of cards available.
Formula 1. Old Waddingtons game which has been reinvented in Formula D. the basic game works well with a bit of fun - not much replayability compared with modern card/board games but still works well.
Risk: We all know this one. We play with old rules and include objectives which makes it a little more strategic - doesn't work well with two players (And Mrs A. does;t like it
).
Cranium / Pictionary / Articulate. Has to be 4+ players.
Trivial Pursuit: Not played this for a while but we have five expansions which helps. Again, the more the merrier.
Pass the Pigs. Always a good standby when we don't want to think about strategy - just good fun.
Sequence. Awesome card game - strategic and as fun with two players as with six.
Bananagrams: Good fun for wordsmiths.
Scrabble: Old favourite.
Backgammon / Othello / Chess: two player standbys but obviously not card/board games in the strictest sense.
Game of Life. Last played this approximately 1985 so can't comment