I took 2 years of Latin, 2 years of Greek and 2 years of German in HS. Latin taught me more English than any English class that I ever had. The one thing that really comes to mind is the difference between who and whom. No one could ever explain it well enough until I took Latin. When we were learning about the ablative and accusative cases, it all clicked.
Believe it or not, Greek really helped me learn the Russian that I know. This is not because they are both based on the same style, but because learning to read in Greek in HS helped me to better understand the Cyrillic alphabet. I wasn't afraid of it. I can still bless myself and recite the first 4 lines of the Oddysey in Greek. It also helps to know these other languages because you can record your passwords on paper without the fear of most people being able to read them.
As for German, I can say, 'I don't know,' 'I don't understand,' I can order beer, count and say the alphabet. That's about it. So much for German.
I want to learn Spanish.