The short answer is all of Brian's stuff written on guitar. Freddie's piano compositions are in trickier keys. Most pub rock bands do 'tie your mother down as it's a simple riff on the open A then it's G-D-C-G. The solo is played with a slide and that's a skill in of itself.
Fat bottomed girls is relatively easy and fun also:
This chap's rather good at teaching Brian's stuff, and a friend of mine to boot:
If you follow his channel, he's worked his way through most of Queen's back cataloguehttps://www.youtube.com/channel/UCQYskKOAwn79enMispbgh_w
An exception to this rule is: The easiest Queen song is Crazy little thing called love. A riff over a D major, with a little finger augmentation (easy) Then G-C-G-D then the turnaround B(flat)-C-D
This dude nails the solo:
This chap's not too shabby either: