Top 10 Differences Between Pokemon Red/Blue and Pokemon FireRed/LeafGreen

Charizard can't learn any Flying type moves in Red, but can in FireRed

Pokemon FireRed has Dark and Steel types, Pokemon Red didn't

The starter Pokemon can learn some moves faster in FireRed than in Red

Psychic type Pokemon are immune to Ghost type Pokemon in Red while Psychic type

Psychic type Pokemon are immune to Ghost type Pokemon in Red while Psychic type Pokemon are weak to Ghost type Pokemon in FireRed

A couple of moves had near endless critical hits in Red, but in Fire Red those

A couple of moves had near endless critical hits in Red, but in Fire Red those moves had a critical hit once in a while

Charizard was weak to Ice type moves in Red, but in Fire Red Charizard is neutral

You have more to do in FireRed than Red

There's a VS Seeker in FireRed, there's none in Red

The graphics are easier to see in FireRed than in Red

In FireRed, you get to catch some generation 2 Pokemon, in Red there's only generation 1 Pokemon