In the following post we've got a few benchmarks, one of them not quite entirely ready for dual-core (Quadrant Advanced,) and a couple that are. What you're going to find is that this T-Mobile G2x is a beast and can chew up and spit out basically any other smartphone you're going to be able to throw at it. Have a look and notice the other veeery similarly titled phone that's in contention with this one.
We're using two tests here besides Quadrant, which even unoptimized for dual-core shows a fairly decent score. The other two tests are MANDRO Bench and Smartbench 2011, both of which show the TRUE power of the force. The great thing about Smartbench 2011 is that it can actually handle up to quad-core systems by natively using 4 threads for CPU-related test. What it reports are two scores: productivity and games. As you run the test, the results are automatically submitted to the general public via Smartbench's website. As you can see, G2x is doing very well for itself.
Next is MANDRO bench which, interestingly enough, shows you what you'd get with a single core on your device vs what you're getting with dual core, then shows how well you're doing compared to the rest of its stored dual-core scores. We've done its Comprehensive Benchmark option here, it therefor running all of its tests 5 times, the scores averaged to get what it considers a fair result. Go go LG!
BONUS: actually should have done this in the first place - Linpack: