Depends on your budget. The pirelli p4 is a nice tire, excellent all weather traction, smooth and quiet, 99,000 mile warranty, and about $115 per tire pretty reasonably priced. Falken makes some cheaper ones that are pretty nice, about $75 each.
They were the most bang for your buck when I got them, not the best tires I've ever had, but for the price they couldn't be beaten. The best tires I ever had were bridgestone potenza RE910's, they stopped making that model years ago, but they just would not let go.