Thor
I tend to lean towards Thor winning. If he took it way up and went into warrior madness I could see him winning. However this may not be the case, and if not he would lose to Superman, while breaking even or outright defeating the Surfer.
Superman
Everyone knows that Superman's combat speed far surpasses the others, so if he is going all out but retains his analytical mind, he would defeat Thor in many scenarios. He would then be able to turn his attentions to the Surfer, and with extreme luck defeat him. He would have to get in close and overwhelm the Surfer to sweep this IMO. If not he's toast.
Silver Surfer
Like I mentioned earlier; Thor and the Surfer break even, or Thor magically defeats him with Mjolnir. While Superman takes a normal Thor with difficulty. The Surfer on the other hand has the ability to do a number of things to Superman. He could siphon off the solar energy in his cells, make it so that Superman reaps no rewards from solar radiation, or do something even more devious. He could literally make Superman allergic to solar radiation by altering his DNA slightly.
In Closing
My vote goes to the Surfer, but it would depend on who is dog piling who. Thor, and Superman may just decide to overwhelm the Surfer from the onset. The variables are too many to really give a solid opinion on which one of these guys wins the majority. Thor defeats Surfer, Superman defeats Thor, Surfer defeats Superman. Rock, Paper, Scissors.