Which of those four games—Ticket to Ride, Stone Age, Dominion, and El Grande—do you guys prefer?
Well, as Steve has posted elsewhere, I'm actually a bigger TtR fan than I'm a Carc fan. If you are getting that, definately go for the US map with the 1910 expansion, but that is only optimally played by at least 4 players. The European maps are really optional (Marklin introduces train stations, Nordic has a long route, Switzerland has destination tickets, all 3 have some combination of tunnels and ferries), but you may want to get them if you usually play with less than 4 players - Switzerland would be the best map IMO for 2 - 3 players. Skip the dice and the card versions, they are IMO inferior to the base game, unless you are the type that actually prefers dice throwing to card drafting.
There's a whole thread on Stone Age I think...