There's many options. Here's a quick run down and my personal thoughts.
onArcade $67: this is my personal favorite. High scores, commenting system, user system, and overall clean code and setup.
Arcadem Pro $20: I run this on a few sites. It's pretty good, nothing special though. Nice Ajax interface and pretty easy to install new games from sources like Mochi.
AVArcade $10 or free: I run this on quite a few sites of mine. These are mostly sites I get a good domain and just set it up quickly. In the long run, I don't think I would run any high traffic/earning sites on this. less polished than others but still a good starting point.
ArcadeTradeScript (ATS) $75: This is a good solid script. Good interface, and the greatest benefit is the trading system. These days a lot of arcades struggle getting traffic. Unless you have rock solid SEO and can get a good 5-10k visitors a day, a lot of people turn to traffic trading. You essentially pay for traffic, and trade it among sites. Buying 500 visitors with trading, in theory, can turn into 1000 or even 1500 visitors with trading. Easy to lose money with this as well though. I run this on a couple sites, it's not perfect, but solid. If you decide not to use trading the rest of the script is pretty good as well.
Here's some samples I run:
onArcade: hubits.com zamped.com
I guess I would recommend onArcade if you have no interest in trading (more quality site here IMO) and ATS if you want to trade (less return visits and more focused on income). Lots of people make lots of money trading and without. So up to you.
I suggest you check out the forums: Talk Arcades if you're more interested. Huge amount of information there for arcade webmasters.