To combat this, I try to keep the game moving at a good pace. This is possible because I don't have to spend time describing the appearance and function of many of the items and locations. If you can't keep the game going with atmosphere then keep it going with plot and action. The problem is, burn-out usually tends to come sooner rather than later because of the pace.
My answer to that is to throw out the rule books. Be more forgiving to the players, allow them to do James Bond-style stunts and Indiana Jones-style rescues. The more latitude they are given, the more 'into' the game they will get.
A great way to get past this problem is to have a deep well of imagination, which is why I started GMing in the first place! Fantasy and Sci-Fi games open up many possibilities in their own realms of fiction, but contemporary games consist of the same setting, the same world, the same attitudes. This can limit the adventure, sure, but it can also help you in your quest for a new idea. After all, the world is set and you already have your guidelines as far as the setting goes - all you have to do is come up with the plot. Sure, the game may be another murder-mystery, but it's the reason and circumstance surrounding the murder that makes it unique.
My favourite idea is turning the world up on its head. A vast plague leaving few survivors, a new Ice Age, a holocaust, an alien invasion, the Rise of the Machines... You take the world and twist it all out of sense and proportion. This works great because then the rules don't apply any more. There's no restrictions on society or law, and you can change the rules to reflect that.