It's way more stable than most other coins and can be used in a lot of places (most coins can't be used anywhere outside of exchanges). Being less volatile also means that it's less like to to x2 - x10 any time soon, but it's a solid investment right now (or well, right now it might be a bit more expensive than usual due to the fork coming up).

I seriously doubt any of the other coins will ever be as big as Bitcoin, but time will tell I guess. EDIT: Well I guess that if China goes and assigns a "national cryptocurrency" or something that one will likely explode and could compete directly. I don't think anything else could come close otherwise.