The game seems to end after a few deaths, no matter how many credits you put in. Is there any way to cheat this?

Obvious answer is to get better at the game.

If you're using MAME though, use a cheat.dat file and enable cheats and enable infinite lives (so you can still get hit and die. Infinite credits in MAME is like infinite lives anyways).

I think Rocky music helps in the training to get better.

The more you play, the better you get, simple as that.

Good luck.

So even in the arcades, no matter how much you put in you still can't beat the game if you suck?

If you can put in some credits and it goes over, its somewhat reasonable. But yes you can't beat the game if you're not good at it. There are DIP switches that the machine operators can set to set how many times you can continue or whether or not you can continue at all. Gaia Crusaders (another beat em up game) won't let you continue at all by default. So Unless you're extremely good at beat em ups, you only have one shot.

I found the switch and turned off the continuation limit.

Most games have default set to no limit.

Thanks.