You are correct about technological advances as far as battery weight is concerned, but just make a battery price (as in EUR per kAh) comparison!
I made one, apparentely the cheapest battery technology is still [sealed] lead-acid. That already makes motorcycles too heavy and travel cars too expensive. City cars could live with SLA quite alright.
IMHO it all boils down to this - you want to carry around a few megajouls around. You could store them in a ready-to-use form (kinetic or capasitor), a nearly ready-to-use form (rechargeable battery), a sortof-ready-to-use form (hydrogen, combustible fuel). Depending on which you choose you have to use an appropriate engine to spin the wheels.
You also want to carry that energy for a rather long time (say, leave your car for a week) and safely, or rather in a controlled fashion. Current energy control tech doesn't really let us use kinetic storage (friction) or capacitors (leaks), makes rechargeable batteries expensive (expensive chemicals and manufacturing processes) and is completely up to the mark on combustible fuels (neatly stored in a can), plus the advantage that you don't have to carry the oxydizer (or it's equivalent in a battery).
The whole point of membrane based energy convesion (fuel cells, later bio-stuff might be possible) is to get rid of the piston engine, which is inexpensive (10% of car cost?) but unfortunately noisy (could be dealt with) and dirty (this too I reckon).
The whole point of using hydrogen (with fuel cells or internal combustion engine) is higher energy density and possibly cleanliness.
The two points of alternative fuels (natural gas or produced by decomposition, vegetable oil) - oil dependency (political) and renewability (still too expensive).
The point of alternative modes of transportation (whether rollerblades or metro) is to get rid of obvious inefficiency (1 ton car carries 100kg person). However why should we be efficient when technology already allows us to be lazy?
In short, in the past you had to carry a horse and a haystack as an energy source, now you do fine with a combustion engine and a can of hydrocarbons, in the future you'll get your electric and cold fusion.
just try to live long enough.