I think Mustaine only became a quality guitarist when Marty Friedman joined Megadeth and started giving him free lessons:-) So Far So Good was devoid of good solo parts and all of the best leads on Peace Sells were by Chris Poland. If you look back to Killing Is My Business, Mustaine was brilliant at rhythm but horrible at lead. At the time, Hamett was a far better player, leagues ahead of Mustaine and fresh out of lessons from Satriani.

I do admit though, Mustaine definitely improved with age whereas Hammett went downhill in a big way after Justice For All. What also tips the scales in Mustaines favour is the fact that he's not afraid to try something new and he always likes to challenge his ability... I saw him live years back on the Rust in Peace tour... man I still can't get my head around how he could play tracks like Polaris while singing at the same time... the mans brain is wired differently that the rest of us, that's for sure.

The fact remains though, ALL of Megadeth's best leads, without exception, were played by Marty Friedman. What makes them more impressive is that he was actually holding back compared to the crazy stuff he played with Jason Becker in Cacophony.