wow...so many options, and none of which are bad.
i'd have to say missionary is most intimate. if i want to "make love" i do it missionary.
if i want to last she'll be on top facing me. i've also been told that i look the sexiest when i finish in this position.
reverse cowgirl is amazingly hot as well, but you lose the intimacy that being face-to-face provides.
as far as doggie and all it's variations go (her being flat on her stomach, the spoon position, etc) i enjoy them too much for then to be my favorites. aka i cum too quickly.
so to answer the question at hand i guess i'll choose being on bottom with her facing me as my favorite. it's still very sensual and personal, and i like having the freedom to do what i please with my hands. so there you have it.
as far as i can tell though, there is no bad position.