The SGS3 is the best choice IMO. Why do you think the SGS3 is the only real seller in the Android market right now? It's because it's reliable, has gotten the best reviews from tech experts and is the most ergonomic and appealing to consumers.
I would stay clear of the Optimus G because it has LG software. If you want the Optimus G, get the LG Nexus 4. Exactly the same phone but with Google optimized software. And you never have to worry about Android updates.
Whatever you do don't get the HTC One X+. HTC phones have many problems like WiFi death grip (basically can't connect to the Internet sometimes) because of poor antenna build quality, not very ergonomic and can only record videos at 19 FPS not 30 FPS because of poor camera build quality.