My father taught me to ride on his '84(ish) Manga 750 (this is about 1989/90
Moved to New Zealand for a short time (1990), got my license and a 1988 GPZ250
Moved back to the US is '91 and got the Manga from my father
In '93 I took a CBR600F2 off the showroom floor as my first new bike.
So the Magna was the first bike I rode with the GPZ250 being my first bike I had for myself and the CBR being the first new bike I got for myself.
First bike was ... a scooter Mom wouldn't let me get a motorcycle (age 16), so got a Honda Spree.
When I was 18, a friend had a CB750 that I really learned how to ride on and the next year after I moved to Seattle, I got a 1978 Honda 400 twin (blue). That thing was a tank. That Honda was really my first motorcycle. Rode it all over the PNW.
First bike was an IT125 at 14.
After that a Boxoa 175 (russian bike that simply refused to die).
Then a 2001 R6
After that a 2005 R1
Followed by a Pani v4s
a Pani V4 SP2
and now a Pani 30 year limited edition SP2.
First was a '76 Honda Z50A, when I was 6 years old. Still have it in the garage. If you mean first street bike, that was a '92 Suzuki GSXR-750 purchased once I got my first real job after college.