Queen On Fire – Live At The Bowl is the best official CD – quality wise and performance wise. But the setlist doesn't appeal to everyone, because there's a lot of Hot Space stuff and some of the great earlier songs are missing (The classic medley, R 'n' R medley, KYA, DSMN...). But in fact the performance is absolutely awesome, they could have played only Britney Spears songs and it would be worth listening ;-)
Live Killers has a great setlist, the performance is very good (but at some points overdubbed or at least mixed together from different sources) and very powerful, typical for that era. The mixing of the different venues is done very professionally, I didn't recognize at first.
But there's one bootled from the Live Killers era that beats it by far: Hammersmith Odeon 26.12.1979. Freddie's performance is top notch, there are some surprises (Silent Night) and also an awesome rendition of Crazy Little Thing Called Love and Save Me, both not yet ready for the Live Killers album. The sound quality is excellent, too, so it's my all time favourite Queen concert!
The We Will Rock You CD is not bad, but not really exciting either. I like the setlist, the performance is very good also, but it lacks something. Don't know really, what it is.
Wembley is a great concert with an enthusiastic audience. Personally I like the 70's songs better, but it still is a great CD. But if you can get hold of the Budapest gig from the same year: That is an even better performance!
There are some 70's bootlegs I can recommend:
1. Live at Hammersmith Odeon 24.12.1975. Famous gig, very interesting because of the "old" setlist, but including BoRhap already. Great performance, perfect sound, and available on video also!
2. Live at the Summit, Houston 11.12.1977. Great performance, very nice setlist – a transition between the "classic", pre-Champions setlist and the Live Killers era – and excellent sound quality with the only disadvantage of much too less audience noise. That's a real pity.
3. Live in Chicago 1980. Great gig, excellent sound, nice setlist.
... I'll be back again before it's time for sunny-down ...