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hmmm if I had to choose my favourite fight would probably be goku vs cell. That was a really even fight similar to the ones from Dragon ball. Following that I think a lot of the buu arc fights were pretty spot on.
i honestly found the namek saga to be really good (in dbz kai), it kind of had this desperate feeling all the way through where you werent sure if a win was possible.
DBS is looking pretty sweet atm, animation has been a bit iffy at times but its definitely not bad by any means.