The only one worse than McCain was Romney.
I don't see any of them doing better than McCain. Guiliani would have been popular in the North East and California, but he would have had troubles carrying the Midwest and South. Huckabee would have had no support outside of the Religious Social conservatives, which wouldn't have been nearly enough to win. Romney would only appeal to the North East, and he would have likely gone no where with the rest of the nation, Alan Keyes would have had the same sort of support as Huckabee. All in all, not a single one of them would have pulled more votes than John McCain, so I don't see how you can say they were better candidates. Of the whole pack, the only good one we had was Fred Thompson, but he didn't get into the race early enough, and then he didn't put out much effort in trying to win the Nomination.
Out of the lemons we had to work with, John McCain was the least bad. If you feel otherwise, I cannot comprehend how.