There's plenty of sex in LOTR. I've been in love with Aragorn for years. I haven't seen the film yet, so I hope I won't be disappointed. I'm glad to hear,though, that my imagination is not going to be stunted by someone else's version of the gynaecological details.
So there aren't many female characters. The few female characters are larger than life, each representing a particular virtue; Galadriel - wisdom, Eowyn - courage, Rosie - domesticity etc. I don't find the lack of females a problem. I can identify just as well with the male characters since they have qualities which we can all share.
By the way, does anyone agree with me that Jane Austen was one of the most erotic writers ever? 400 pages of build-up and then.....well just imagine.