How about 37°C at idle,
that's with a room temp of 23°C at the moment. Then again for the most part idle doesn't mean much as it is the load temps that are the most important. At the current room temp mine tops out around the low to mid 60's depending on the game.
One thing that a high idle temp can indicate is as mentioned the fan is full of dust. It can also mean as mentioned by clearfire62 that the thermal paste isn't any good any more; a lot of the card manufacturers aren't known for using the best paste.
Another thing it can indicate is that the card isn't going into low power mode when idle and staying on the full 3D clock speeds.