This is a tough one because D&D came into my life in its (relatively) early days around 1980-81. Many of the other games mentioned didn't come along until much later.
Without D&D to bridge that gap, I may not have gotten into roleplaying games at all. I'd probably have made different friends and gotten involved with the "wrong crowd". Soon I'd have been drinking all weekend and getting high in the parking lot of the school at lunchtime.
I'd start sleeping with women of low morals and then, on a whim, I'd steal a car. After that I'd spend some time in juvenile prison and jail for a few years before being released and taking some kind of minimum wage job as a dockworker. There I could make enough money to buy cheap beer and live in a van down by the river. Any day now, somebody would find me dead from a crack overdose, lying in a pool of my own tepid filth.
Either that or Rolemaster.