*shrug*
Tolkin really doesn't have anything in the way of major female characters. He's got a couple female elves that show up and whatnot, but none of his "heros" are female.
It's not something I think of as offensive. He's a male fantasy writter from another generation. Most male authors do have more major male characters then female, while most female authors have more major female characters, and the primary character is almost always the same sex as the writter.
Which is not nessasarly a bad thing. A lot of times when I read a about a main character written by the oppisite sex, the character falls flat or is a bit odd. I don't think that's sexism, just an example of the difficults in writting fictional characters.
I havn't ever read Austen, but I have read a lot about that period, other novels set in that period and a LOT of romance.
And no, men are not generally the primary character, nor do most authors take much time devolping the few male characters (hell, some don't take any time devolping the female characters)
I think those books set in the Regency period and Victorian era can get away with it a lot more, simply because the sexes were highly segregated and the society was so stratified. Higher class young (unmarried) women didn't spend all that much time with men outside of their families and didn't spend too much more time with the ones they were related too. Exposure too "eligable bacholers" was highly regulated and observed.
Not that Austen was really a member of the society she wrote about (she was gentry, not nobility BIG DIFFRENCE)
As for why it was (and remains) so popular. Orginally, her books were quite scandolous. They were published annonamously and it was clear they were written by a women of the higher class, which was huge. Secondly, the books depicted actions, decisions and ideas that where not entirely welcome. Marry for love, instead of station and what you're parents want!?! OMG!!!
They remain popular because a.) They were a big deal when they first were released (and even books that suck can remain a big deal if they start off with a big enough bang) and b.) Because a large majority of women like fluffy, unrealistic romantic doggerly.
And before anyone pokes a fun at the b.) reason, I will point out that men seem to enjoy some pretty mindless novels of explosions, gunfighting and grabbing booty, so the sexes are still running even on brain fluff reading material.