For what it's worth, they have some truly epic stories and characters wrapped up in them (alongside other less interesting stories, at least in XIV's case - I can't recall much on XI).

Also, for XIV at the least, it's super-easy to team up with randoms, complete a dungeon and then forget about them forever. It's very rare that I ever have any issue playing with randoms, sometimes I find it a bit easier in that you don't have to try and get friends grouped up at the same time. You just crack into the duty finder, complete, and you're done. I still rate XIV as one of the better games in the series and my experiences of XI were pretty great too.

Personally, when I consider which games I have "beaten", I just focus on the main story of the original game and nothing more than that. Expansions are expansions, and while they are often better, I think it's fair to say "I've finished all the numbered FFs" if you have done the initial storyline. Having said that, I'll repeat that the expansions are often better, particularly in the case of XIV. The Heavensward expansion was awesome.