What variety of basil is best to use in cooking overall (not just Italian)?

Genoese Basil is the best for all around use. Seed can be purchased from www.johnnyseeds.com
I like "Siam Queen" for Asian cooking. It's delicious and very ornamental.

Depends on what you're making! Thai basil, for example, is wonderful in Thai food but tastes perfume-y (at least to me) in Mediterranean.