It's sad, from a genetic point of view, that Frodo did not marry or beget children. Though his genes were present in the community, this one exceptional individual may have changed the overall disposition of the Hobbit 'pool.' Sam's children were exceptional; how much better those of his Master?
I can understand why Frodo did not marry after his return - too messed up both physically and mentally to attend to such matters. Plus, like his uncle, he had seen female elves, and after that there's no going back to Hobbit women. But beforehand, if Frodo was not considering marriage, was there at least some lass he was becoming sweet on?
And to think that, after losing the One Ring in the Sammath Naur, he could have come home and put on one almost as terrible (i.e. ever misplace your wedding band?
).