For my part, Intel is the way to go - no question. Further, I think dual-core is the sweet spot right now. Quad-core sounds cool, but I don't know that enough games will really make use of it (Alan Wake for one will, however) and may not ever. I'm tempted by dual-core extreme but that really jacks the price up and while the performance is better, is it 'better enough' to justify the increased cost? Dunno. I think that's a personal decision based on your budget and how long you want the machine to last.
As for motherboards, I like Asus and Abit - just pick their most current one with the features (SLI, RAID, SATA, on-board audio/video, etc) you need and there ya go.
ASUS has a series of products called The Republic of Gamers and there are some good products in that lineup.