Yes, I agree, its energy density is lower than gasoline, but still better than most electric alternatives at the moment. You also don't have to stand around for hours to recharge your energy supply when using gas.
I don't think that electric alternatives will be very successful until we see all the energy of a present day car battery squeezed in a form factor of something as small as an AA battery (for example).
As for availability of gas, the last estimate I read said that there is enough NG in the world to power the planet for another century at-least, thanks to fraking techniques making previously unusable gas deposits available for extraction. Right now, NG is about to to become very widely available - and subsequently, very cheap as well.
There are still other technical issues like safety, and even others, such as security.
Here in Israel, if you drive a gas-powered car, you aren't allowed to park it in public underground car parks, for example, for security reasons. I'm sure that there are a few other not-so-obvious considerations as well, but I think that legislation and safety and other challenges can be overcome in the long run - at least more easily than those of hydrogen. Gas can make a viable bridging alternative to hydrogen and other options until they mature a bit more.
I would also invest heavily in battery tech, because that is really what's holding back electric cars right now IMHO.