GameEx is extremely skinnable, and has integrated tools available for tweaking or constructing themes. Here's a theme strongly inspired by the look and feel of Maximus Arcade:
Here's a download link for that theme if you're interested:
Maximus Arcade theme?Like gamepimp, I was a long time MA user but jumped ship when mameseer stopped supporting his product (according to many reports he continued to accept payments despite being extremely slow to send registration codes, that is if he bothered to send them at all).
Now I couldn't be happier with GameEx. The support you receive is second to none, and Tom Speirs (the developer of GameEx) is
extremely responsive to user feedback. The occasional bug report is typically dealt with in hours rather than days. There are definitely a lot of features available in GameEx, but it's all very configurable and you can typically disable any functionality you're not interested in (you can even install GameEx Lite if you're truly only interested in running MAME and a handful of emulators)