I am an expert on this =P
But you can't just say "This is the best motherboard EVAR!!11!"
You have to look at the whole system, the motherboard must have enough pci-e slots for you, it has to support the chipset for the processor you want, it's got to have enough PCI slots so you can run what you need to run. It needs to be the right form factor for your box. Some people build backwards, and build everything but the mobo, then at the end, go find a motherboard. Some people build from the motherboard, all the way out to a box.
Personally, I pick the processor I want, I find a mobo that will support it, and then I decide at that point, whether I'm going to do SLI, or how many peripherals I'm going to be connecting and especially which box I'm going to use.
So if you come back with a bit of the other information, then I'll go ahead and help you out. But you can't just say "best mobo evar"