I quite enjoy having my wifey on top, and its good for her. One thing we do, is have her sit up on me, then I can play with her clit while she grinds on me. We can nearly always get her to cum like this, but I find it difficult to get there, so we generally have to change positions after she cums.
Reverse cowgirl I find very good for me, although she doesn't cum so easily, probably because she's used to cumming with me rubbing her clit while she pumps away, and its not so easy to get to with her acing away. She has got a really good motion in this position though, and it can be a really good orgasm for me.