I always thought I loved pizza because I like the individual ingredients, so naturally I would enjoy them all baked together.  I guess there's more to it than that.  The American Chemical Society actually broke down why pizza is so tasty.

Apparently I really like pizza because of the Maillard Reaction.  According to the video  when something is cooked to above 140 degrees celsius, the amino acids and sugars react to create flavor compounds that give the food that 'distinct bold cooked flavor.'  The Maillard Reaction is also responsible for the color of beer, chocolate, maple syrup, and coffee.  Toast and the flavor of roasted meat are also caused by the Maillard Reaction.

So, I guess I can blame the Maillard Reaction for causing me to have pizza for dinner on Friday night and Sunday night, oh yea, and leftovers for lunch today.