I think everyone has a different definition of their first love, for some it could be the first person they dated.. For others it could be the strongest, most real and deep relationship they've ever had.. So yeah.
I wouldn't say the first guy I ever dated was my first love. I'd say your first love is the first person you have fallen in love with and grew to have really strong strong feelings for. It's something you just can't forget.
First love. It's the person you'll compare all other partners to. It's not to say you'll always love them, but you'll be a bit hurt when they get a new girlfriend, or you'll follow them on Facebook or Instagram