Is this good enough to be a new gambit? 1. e4 e5 2.Nf3 g5

I think of this as some weird, black side Vietnamese gambit, really risky.

I mean, TECHNICALLY you could call it a new Gambit, but just because g5 is legal doesn't mean you should play it - it is definitely NOT GOOD!

It would be the equivalent to "Just because they make it in your size doesn't mean you should wear it." Your 2...g5 would be the equivalent to seeing Chrissy Metz or Rosanne Barr in a 2-piece!

this is really bad move

Yo, ThrillerFan, I just ate breakfast. C'mon man, now I can't unsee that and even my retinas are going to need therapy.

Reminds me of like a reversed Grob but a tempo down.

not exactly. g5 is completely useless but to make your king more easier to be attacked.