Well, according to the Road & Travel Magazine, it is this year, the Audi R8.
I could probably agree with that.
Here's the list for the past few years:
2008 Audi R8
2007 Jaguar XK/XKR
2006 Pontiac Solstice
2005 Chevrolet Corvette
2004 Cadillac XLR
2003 Nissan 350z
2002 Lexus SC430
2001 Chevrolet Corvette Z06
2000 Porsche Boxster S
TNT..your rides sex appeal is getting old now
BTW...the Road&Travel guys do rank quite low on my scale of auto-journalism, but hey the stats are funny (and catchy).