I think there may actually be some weight in the comparison of the two.
Al Davis is Al Davis. Vince is Vince. The two aren't very similar personally and have their own legends about them. However, each of them share two traits:
1: They revolutionized the sport/product that they promoted
Al Davis, among other things, single-handedly forced the merger with the AFL which brought us the NFL as we know it today. By his cunning alone he changed the landscape of how the sport was run on a national level. Also of note was his hiring of the first Hispanic and Black coaches in the NFL.
Vince McMahon on the other hand took what was at the time a region based way of doing business and pushed it to a national level, bringing Wrestling to the highest highs it's ever seen. He made wrestling an household topic. Then, in the 90's, he tweaked the formula to bring his creation to even bigger highs. The things the WWE/F started doing became standards within wrestling, from the high quality presentations to "trons".
2: Each of them are/were seen as die-hards and old men out of thier time.
The same things that made Al Davis great made his legacy become tarnished in the end. His unwillingness to change and his "stick to my guns" mentality help ensure that his Raiders never won an NFL Championship since 1983. The Raiders, and Al Davis, became a league-wide joke; an organization and a leader out of time which could never change to keep up with modern advances, always staying two steps behind.
Vince fields similar criticism. After the folding of WCW, wrestling's popularity in the mainstream took a hit. Many people now will blame Vince for what they call "sagging ratings" compared the the halcyon "Attitude Era" days, but that's not really being fair about the situation. Vince, like Al, often has a reputation for micromanaging behind the scenes, often going over everyone else's heads to ensure that he maintains full control of the product, for better or worse.
So is Al the Vince of Football? Is Vince the Al of Wrestling? It may not be a fair statement to make either way. But the two do certainly have a LOT in common.