Its got alot to do with the attitude of teams that play a particular form of the game. e.g.
- PAK fancy themselves as a brilliant T20, decent ODI & avg test. side. ENG are a decent T20 team, avg ODI side & brilliant test side.
- IND are decent in T20, brilliant in ODI & tests.
- SA are gain brilliant in ODI/tests & decent T20 side.
In the past, before T20's arrival in 2007, you had to be a brilliant ODI/test side(like WI/OZ of yesteryears) to be world beaters(the best).
Similarly if ENG are to lay their claim to that number one tag they have to be better than most in atleast two forms of the game which they definitely are not at the moment !
There really can't be a seperate test/ODI Numero Uno & unless T20 replaces ODI cricket or substantially eats those fixtures you won't have a clear winner in that format cause its like a jackpot on most days.
BTW ENG are inconsistent to say the least if not downright poor in ODI's & you can't use that lame excuse of test cricket being the real deal cause at the end of the day its an international cricket match & if you ain't good at it then just admit your fault not look for silly excuses.