Such an open ended question. All of the bikes listed are great bikes for the type of use you've described. I personally like the Specialized and I'm sure there are a couple in your price range. Their FSR XC line starts at $1,200 USD, and goes up from there depending on the components you desire.
The Gary Fisher Sugar 3+(additional 1.5 of rear suspn travel to bring it up to 4" front and rear) starts at about $1300 USD and the price goes up from there.
Since Trek owns Gary Fisher, the Trek Fuel and the Sugars and based on the same concept, just with different linkages and shock positions. Which is better? Depends on what you like in a bike. The Sugars tend to be stiffer and more race oriented and the Fuel tend to be good "all arounders".
Giant makes a very nice full squishy XC bike. The XTC NRS, that is very competitively priced with superior components compared to other manufactueres. There are four levels depending on how much you want to spend. For MY (more all around, less racey) preference I would rather get their AC Air, it's more of a lighter weight freeride bike! If that makes any sense at all!
Cannondale's, their Jeykll is a great all around bike with an adjustable shock mount that allows you to change the bottom brackett height and the head tube angle simply by rotating the rear shock in it's trunion mount. The big thing with Cannondales are their forks. People either hate em or love em. Personally I think they are great! The steering is very precise and due to their design there is no lateral flex, heck there is no flex at all regardless of direction. Problems are the limited travel, unless you go with a LEFTY and then that's an entirely different subject all together!
Santa Cruz bikes have been gaining a lot of popularity due to their simple single pivot design and excellent craftsmanship, although pricey! A superlight frame alone can run $1,300 to $1500 USD.
A company that doesn't get a lot of press, but has some very nice bikes at great prices is HARO. They've got their Werks line of bikes that are all race quality and have a great component spec. Their full suspension is basically the same as the Santa Cruz superlight without the high price.
Just my .02
Good Luck
L8R
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