One of the most popular PC benchmarks now available for thousands of different Android devices
3DMark, which has been one of the go-to programs to determine your computer's graphical performance is now available on the Play Store to evaluate phones and tablets as well. The app is nicely designed and gives you more than just the ability to run benchmarks. You can get a nice breakdown of how your device has performed, with metrics on the score, FPS for different areas of the test and details on how the device performed compared to other people with the same device. You also get a full set of leaderboards for the best scores recorded on different devices.
The app is quite a large download at over 280MB, but if you're serious about your benchmarks you'll want to have it at the ready. Grab a download of the first version at the Play Store link above.