The best oil filter in the business *was* the ACDelco Ultraguard Gold.The Ultraguard Gold was an example of what big development dollars can do. It had outstanding filtering ability very low resistance to flow and excellent bypass characteristics.
Unfortunately ACD did not have success marketing this product so, other than the UPF44, which fits LS1/LS6, the Ultraguard line was discontinued about six months ago.
My latest research shows there are still some WDs around the country that have remaining stock of some Ultraguards. UPF1218 fits many small-blocks and big-blocks. 92 and up LT1s take the UPF52.. If you can find any of these filters, buy them. Best thing to do is locate a friendly GM dealer or ACDelco auto parts retailer and see if they can find a WD with some stock.
I think the next best is the K&N Performance Gold. It is not actually made by K&N, but "private-labeled" for K&N by a major mfg. of filters. It's pretty good from a filtering and restriction standpoint.
I've heard good things about the Mobil 1 filter except for it's cost.
The standard ACDelco Duraguard filter is not bad.
As some on this thread have already said, some of the Fram products leave a little to be desired.