The only way to make this game worse would be to make it cause your Gameboy to stop functioning correctly.
First I'll talk about the horrendous graphics. You have Vegeta with a head about as big as the rest of his body first of all. That's probably the most memorable thing about the graphics. Everyone else looks kind of clunky or inaccurate or ugly. The backgrounds aren't anything you'll want to look at. The special attacks aren't flashy enough (usually I complain that they're too flashy >_>) and overall you'll find yourself wishing you could play this game without looking at the screen.
Moving on to Gameplay.... I wish I could just skip this part to avoid reliving those horrible memories. Absolutely horrible. You have the Health bar and the Ki Bar, just like in the Budokai games (except the Ki Bar only fills 3 times here). Each character has the basics, punch, and kick. The exact button combo for Ki Blasts still eludes me and almost seems to happen randomly for me. Ki Blasts use your ki (surprise) but really, considering their lack of power, are only useful if you want to spam your opponents with attacks from 4 inches away instead of spam them with attacks from 2 inches away. Special Attacks are activated through certain button combos (supposedly) and use your ki as well. Basically the game never tells you these combos so you have to get lucky or spend hours pressing multiple button combos to try to figure it out. there is a bit too much balance in the game. There is little to no difference in damage (except for Bardock of course) and the differences in speed hardly make a difference considering how small the arenas are. There aren't a whole lot of characters to choose from either. The unlockables will probably be able to keep DBZ fans playing for a while but don't provide much fun for other people. There is no plot. You just beat arcade mode with a character and it gives you a paragraph of what happened to that character. Lastly, the difficulty can be hard on some difficulty settings, but waaay too easy on others. There is no good middle.
One or two songs may sound nice and some of the music may remind you of the series. Otherwise the sounds are horrible. Some of the attacks sound like what you would get if you banged a bunch of random metal, wood, rubber, and plastic items together. Others just aren't memorable.
Overall this game just isn't fun, no matter how much you like DBZ (well.. ok, if you are die-hard than you might like it). I suggest you don't buy it and only rent it if you are a DBZ fan who must absolutely know if it's really this bad.