Surfer vs. any individual Lantern: Surfer wins. Reasoning: Although Lanterns are all theoretically as powerful as the Surfer in that they can do practically anything, every Lantern subconsciously limits himself to some extent. Faced with a being as powerful as the Surfer, I think anyone would be pretty scared and doubt their own abilities, which would lead to further limiting of the Lanterns. So the Surfer takes it with relative ease against just one GL.
Surfer vs. the entire Corps: Corps wins. Reasoning: Kyle was more powerful than the Surfer as Ion, and Ion is all of the Corps' power channeled into one person. Take that power and put a 7,000+ to 1 advantage in manpower behind it, and I think it's pretty clear the Surfer would get pwned. Numbers count when each Lantern can do about half the stuff the Surfer can on his own.
Personally, I think the Surfer would tax himself quite a bit against a handful of Lanterns, like say 5 or 6. Upwards of ten or a dozen good, well-trained, resourceful Lanterns and the Surfer's toast, let alone the entire Corps.