Interaction in Race For The Galaxy
While low interaction is a frequent critique of the game, I think most experienced players would tell you that you're not playing the game as effectively as you could. First, I'm assuming you're playing the game without the Brink of War rules which add direct player conflict to the game. Second, a large part of the subtlety of the game is the need to very carefully make decisions about role selection - optimally, you want to balance your selection against the roles you think other players will select while avoiding selections that benefit other players more than they benefit you (in other words, you want to maximize the value/activity you achieve during a term while minimizing the value/activity of your opponents).

Another subtle point is the need to review other player's tableaus for point scoring combos - when you see someone else's combo fall into place, it's generally advisable to move the game to its end (unless of course your own combo is up and running and superior). The last tidbit that is typically overlooked is card denial. In most games of RftG, the deck will be shuffled a few times, increasing the odds that your opponents will get the chance to play rarer cards that can shift the victory point totals significantly. Holding on to cards that you intend to spend for a bit longer can mean that a useful card never sees play due to the timing of shuffles!