At his peak,Botham in my opinion was the best of the lot (from 1977 to 1982)..the thing is Botham wasnt at his peak for a lot of his career mainly due to a back injury,but even in the World Cup in 92 his bowling was instrumental in Englands success in that tournament.
Imran got better as he got older,his batting came on big time when he wasnt bowling as much (due again to injuries)...but when he was bowling at his peak he was amazing, very fast,good swing.
Dev was just a bit below Botham and imran in both bowling and batting.
Hadlee was easily the best bowler of the four (although he didnt have a brilliant record for the first few years),and he could bat brilliantly occassionally,but wasnt consistant enough.
As an all rounder,I would choose Botham (best swing bowler England have had for 30 years, on his day the most destuctive batsman in the world bar Richards,and an outstanding slip fielder,could change a game in the space of a few overs either with his batting, bowling or fielding).
As for Sobers,I never saw him play (apart from odd bits of film).He obviously was an incredible batsman,and a talented bowler.
Many commentators on the game have said that Botham at his peak was as good as Sobers,and I am not going to argue against that.