The question is dumb and so are the answers.

Person who asked this question, should have calculated how many lightbulbs he need to heat up the room - unless he has built tiny room for some pet, then it makes sense to use just one lightbulb.

I would assume, that most of the folks on this site are heating up room using their PC... For me it is clearly a 2-5 degree difference if the room is not heated by PC.

PS Ironically, I use the most energy consuming and brightest lightbulb I could find(among the energy efficient lightbulbs, because there are no other options).