In fact, it is relevent to compare the highest grossing games of all time and include an MMO. You think that COD doesn't pay for server maintenance? You think they don't have updates and DLC? Isn't that an ongoing cost? That's not what the graph is trying to portray. It's simpy listing the video games that have made the most money in history. It does not concern itself with how they went about doing that, only that they did. In fact, games like COD and many of the others on that list have purchaseable post-release content that users PAY for, earning them more gross revenue. So, it is valid to include WoW. Don't hate on them because they are, in fact, the most successful video game in history. You can be jaded by the quality (or lack thereof) of their recent content and let that color your opinion, that's your own loss. But don't think for a second that just because their subscription base is rapidly shrinking that they aren't still a massive legend. WoW will eventually cease to exist, but when they finally shut down that last server the can do it with a smile knowing that they set the bar higher than any current (and many future) games will never be able to reach.
As for comments about inflation, WoW has been out for 10+ years and is one of the oldest games on that list. Therefore your argument is made that much more invalid. Newer games should, because of inflation, be that much closer in the standings to a 10-year-old game. But they're not. If you adjust for inflation, I'd wager that WoW would be even further ahead, and you'd be crying harder.