Can a voltage regulator or stabilizer increase voltage and current simultaneously when used with a generator?
A boost regulator could switch the voltage to something higher but at lower current.

A buck regualtor could lower the voltage but increase the current.

There is nothing, though, that will increase current and voltage at the same time continuously.
If you could do that you would have a perpetual motion machine.

As @Russel McMahon says, the voltages you mention say that the generator is pretty much maxed out powering an 18Watt light bulb.  You might get a few more watts out of it before the voltage drops down too low for a normal line powered device.

Along with all of that is the fact that your gernator doesn't provide a regulated frequency, and probably doesn't deliver a clean sine wave - your devices won't like that very much, and might burn out from that or from over voltage since your generator doesn't provide a regulated voltage either.