Music Bands are such a large grouping, that to call any band the best in the world would imply I really know something about who is who in the world of music and I have a wide experience. I cannot claim that for myself. I have heard spanish guitar bands (purely musical) from the 60's that will blow anyone's brain off! I have heard of Naga and Mizo youth play fabulously just in their own congregations or evening 'chill-out' sessions.
So I cannot claim any band to be the best in the world. But if you re-phrase that question then I may say that I love the Beatles as the best in the world. They just pluck that particular string in my heart, and they did strum away at my heart strings when I was way too young, so that I cannot move on to love anyone better than them.
I think I love all their numbers, but I particularly drool over ..'Yellow submarine', 'Lucy in the sky' and 'Hard day and night'.
I do not suppose I would even care to break the magic of that first love by listening to them if they got together now. It never happens...!