Guns suck.
No honestly, just firerate/spread is not enough to randomize weapons. I mean, if there were different kinds of damage (rocket/acid/ice etc.), different range, special effects - then why not. But now, you only need one gun - something with good spread and good damage - which renders ten slots kinda redundant.
Also, names could help identify the guns.
BTW, how is DPS even counted? To target hit by one of the bullets? Assuming all bullets hit a target?
Enemies suck.
They're nothing original - some are faster, some are tougher, some shoot bullets. Done a thousand times. No different species, no weaknesses, nothing. They're dumb and easy to kill.
Arenas suck.
Or should I say ARENA? Since there's one, and very small. And it is too small to allow any tactic beyond "keep the far away with something fast and dodge bullets".
Summarizing - game is severely flawed. If you intended it as alpha/beta of sorts, just a check if the engine works, then I say it was successful. But as full game, it falls flat.