Sometimes though, I just want the game to look like a game. Borderlands hit the mark in this regard. It really depends on the game and what they're trying to accomplish. Many games sacrifice "realism" in their graphics if it doesn't fit their style. Blizzard has never been a headliner in the graphics department, other than their cinematic intros and mid-game cuts, but their games are consistently worth buying since the original Warcraft. A game doesn't require the best graphics to be a joy to play. In fact I would take a hit in the graphics if it means they spent some of those funds on good plot writing and solid voice acting.
Some games do require the realistic graphics to give you the immersion needed to make you continue playing. The most recent Wolfenstein comes to mind.