Yes, Either is to sum types what (,) is to product types.  The difference is that there is no "anonymous" sum type equivalent to (,,) and (,,,) and (,,,,) and so on, which I think is what the original question is getting at.  Indeed, I sometimes wish I could write something like (straw-man syntax):

 foo :: (Int | Bool | String | Double) -> Int
 foo x =
   case x of
     1stOf4 i -> i + 7
     2ndOf4 b -> if b then 1 else 0
     3rdOf4 s -> length s
     4thOf4 d -> floor d
 bar :: Int
 bar = foo (2ndOf4 True)

and have that work for any size of sum type.  But I can't.