Fluorine has greater electron affinity than mercury or tungsten and hence fluorine could have been in electric bulbs.Because it can attract electrons easily than the metals which mostly repel extra electrons, so fluorine should release more energy[light].Then why wasn't it used?
First, you mix two types of lamps: incandescent lamps use conducting material with highest possible melting point. It was graphite at first, tungsten later. Mercury lamps use vapors. Obviously F2 cant be used in the first type. What about the second type? Any material inside of a lamp needs to cycle between to states to emit light. High electron affinity by itself is not necessarily good. Materials that are transparent and can contain F2 are at best expensive or might not yet exist. Glass and plastic will react with fluorine.
People generally need a light of a certain color. They use neon, argon and krypton to get different colors. Mercury works better because it has much more energy levels available, so it doesn't emit a single color, but a spectrum that is close to sum light. The bulb itself is coated to re-emit lite and make it even more "sun like".
As for the light intensity - you can increase it by using more powerful supply of electricity. People do try to increase the yield of light, but it has little to do with electronegativity.