Best? There is no "best", because that term can be relative to "best price", "best performance", "best filtration", "best noise reduction", "best blah blah blah". Then you have the intake setups that incorporate a portion of each of those categories for a good all-around balance.
If you want cheap and easy, and don't care about noise, then go with a Tymar or DIY 6637. It works and filters well.
If you want middle price, quiet, and excellent filtration, but don't have a lot of power, get the Ford AIS.
If your wallet is fat and you don't care about price, like good looks, excellent performance, and good filtering, go with an AFE Stage II with the PG7 filter media.
Of course, there are other brands out there too with similar offerings. Take your pick.
Probably the greatest consensus you'll find on this and other forums is a general all-out hatred of K&N. There are a few people with K&N's and have no problems, but there are others who have had issues, or heard about so many issues that they avoid them all together. I've personally had a bad experience with the K&N drop-in style filter that fits in the stock airbox. I guess "fit" is the wrong term to use, since K&N can't make a filter that properly fits and seals in the stock intake box. That's my rant contribution to the thread.
I've also personally run the 6637 and the AFE Stage II w/PG7. Performance, EGT's, filtration, etc I can't tell a difference between the two. What I did notice a difference in is the noise from the intake. The AFE is still louder than stock, but much quieter than the DIY filters. The AFE also looks cleaner/bling-bling/whatever under the hood.