Do you think the big four of thrash are the height of quality in the genre?

Only twice! Once in Newcastle, England and again in Oslo, Norway ...I was even backstage the second time and caught a bit of them from the side of the stage!

You?
 
Megadeth are my favourite band.

I always liked them the most among the thrash bands I listened to and their Rust in Peace album is easily my favorite thrash album ever.

Great, now I am in the mood of listening to Five Magics! Hehe o_O
 
I think Slayer was the best in the 80s but the other Big 3 were honestly pretty weak. I prefer bands like Voivod, Sacred Reich, and Kreator myself.