I gotta go with ninja on this one... For a beginner though, and comparing you to where I was probably at I would say you're up in the 8's. I didn't really try to learn a lot of stuff when I started. I wasn't that serious with it. But I've been playing for 5 years now and I've finally gotten to where I can play by ear... and learn whole songs in 5 minutes or less somtimes. Those Green Day songs are an example of songs I can learn in less than 5 minutes... Basically as long as it takes for me to listen to the song.

You're moving along a great clip though. I will commend you on that! But keep challenging yourself. If you find those songs easier to learn try challenging yourself with something that might not be so easy for you. That's when IMO you learn the most as a guitarist. When you get yourself out of your comfort zone. Try tackling something like Seek and Destroy... or if you're feeling really ambitious... try starting to learn Master of Puppets. It's a great song to practice on and also grow as a guitar player.