All guys' favorite sexual position is The Reverse Cowgirl except on Thursdays, then, we all dig The Armenian Snow Pal or Classic Missionary. I wish I could tell you it was that easy, but it just isn't so.
Guys are a lot like you and me; they're complex and like various things "best" at different times. For example, one morning I might crave Special K cereal; another morning I might crave Special K with Strawberries cereal. Then, sometimes, I'll wake up with a yen for two eggs and cheese on a toasted poppy.
When it comes to sexual positions, we guys (and ladies, I might add) enjoy a rotating roster of body bumping. We gravitate towards positions in the heat of the moment that express or release a given feeling or desire. What's more, certain positions allow for certain visuals that really get us going. "I must stare at her boobs," "I must kiss her neck," "I must check out my own calves."
I'm surmising you're not just asking me because you're doing a school report and want me to give you the easy answers. I'm thinking you're asking Funny Guy because you want to know how best to please your man. Assuming you're consenting adults and both OK with treating your bodies like the Hamm brothers at an Olympic trial, I think the best way to go about all this is through trial and error. Maybe he likes being entirely cut off from the use of his extremities and is a sucker for the Houdini Triangle, maybe he's a control freak and would do well to experience the submissive role in a Cuban Cradle.
I say try 'em all out and see what makes him feel like Hercules in mid thrust and beam like Justin Beiber when he's done. Try Google cross-searching "Sex Positions" with "Wrestle Mania II" and see what you can add to your collective sex roster.
But remember two things:
1. There isn't a categorical "best," only a best for a given time and mental space.
2. A sex position is only as good as its two position-players. So work together, buy some lube and have fun. Also, stay away from The Boston Jackhammer at all costs, it might sound easy, but its totally, totally hard and upsetting.