Well obviously all songs can be played in all keys. The thing about the C and G key in standard tuning with the keep on trucking sequence - you get that funky alternating bass - plus the chance to do hammer ons with your fingers of the right and the thumb of the left hand. And that wonderful slur on the D on the 2nd string whilst playing the F chord!

If you want that open string sound that you can get with E. Look also at playing with an open D or E tuning. It harmonises nicely with someone playing the key of C standard tuning capo-ed at the fourth.