Being biased, I have to say English. A Yorkshire accent is the best accent, and even better if it's truly dialectal

https://www.youtube.com/watch?v=sB3ieNhEsDY

https://www.youtube.com/watch?v=ScELaXMCVis

I'm not sure why German gets such a bad name, I think it's quite beautiful to listen to. Perhaps it's because they're less bothered about telling everyone else how wonderful their language is (something that in my experience seems to be a peculiarly-Romance trait)? Dutch is hideous though. I also like Icelandic, and Danish can be pleasant enough to listen to. Swedish and Norwegian have an unusual intonation that I find off-putting.