If enough people would be interested to watch people play tic-tac-toe and companies would be interested to invest in it (because they know they'll make profit), then yes I would consider it a sport. However, in this case both of us know that tic-tac-toe can never be a sport because it's an extremely limited and simple game that always has the same course of action and the same outcome when two players familiar with the game play it: a draw. The "skillcap" of tic-tac-toe is so ridiculously low, that anyone who spends half an hour researching it can reach it. Combine this with the fact that once you pit two players against each other who have done this, there's no way either of them can win, and you have your reasons as to why tic-tac-toe is not a sport. There's no way in hell you can compare this to any video game or sport around these days.
Single player games have no competitive element. The only competition you could probably have in those would be speed runs or scoreboards, but those take far too long and have no direct interaction between the two competitors. For this reason I also cannot fathom why people follow stuff as the WoW world first races. So to specifiy my definitions, there need to be a competitive element with direct interaction between the competitors.
Regarding what you define as a professional, fine, label everyone besides the top CoD players amateurs then. That doesn't take away from the fact that CoD would be an eSport. How much of a percentage of the participants need to be able to make a living of the (e)Sport they are competing in to make you consider it as an (e)Sport? All the established sports today started off as tribal competitions with no earnings whatsoever besides perhaps status and glory. Were they not a sport until they became monetized and commercialized, and until people started making a living off of them? Was football just a game until big pools of money got involved? You do consider chess a sport, but how many people really making a living off of chess, which is a game (or sport) that's nearly 2000 years old?
So if CoD would have LoL amount of viewers and prize pools, you would still not consider it an eSport? I don't know, that just comes across as extremely elitist and nitpicky to me.
I'm pretty sure they try to balance and create it with eSports in mind now because they saw the initial reception to their game. I'm not buying the idea that from the moment they wrote down the first line of code for LoL that they wanted it to be a spectator sport. Riot wants to make it one now because they know there's money to be earned. This is why Activision is now pumping money into the CoD scene apparently as you mentioned above.
Norway would probably give you one if there's an established Flappy Bird scene with prize pools and international tournaments. Alas, there isn't because it's a singleplayer game. You can compete through high scores but there's no direct interaction. Regarding Pong, Pong actually has enough elements to become an eSport in my opinion since it's a competition between two players directly interacting with each other. Pong is basically just a basic version of tennis on a screen really, and I don't think you can dismiss tennis as not being a sport. However in this case I wouldn't consider Pong an eSport because the definition of eSports pretty much implies there being a competitive scene with money involved. This is because in case of eSports "games" transition from being "just a game" to an eSport as soon as a competitive scene arises and gains ground, so in my opinion that is an important part of the definition.
I just find it extremely weird when you are talking about those games being partially eSport or have the potential to be one when each of those titles have been proven eSports.
MOBAs also don't show the full picture when spectated. It gets close but you still miss out on info that might be crucial. You're completely dependent on what the observer decides to showcase, and that way you can easily miss important plays. You're pretty much limited to fighting games and FIFA if you want all the information on one screen. Either way, you're putting way too much emphasis on people actually grasping the high level tactics in order to make it interesting to watch. There's thousands of people who watch football and still don't understand offside, or any of the strategies in football for that matter. FPS games are infinitely easier to understand and watch than MOBAs. I personally watch Street Fighter tournaments from time to time, even though I have no idea what the meta is, what the favorable matchups are, who the majority of the players are and so on. Why? Because the game is very clear and simple, you need to deplete your opponent's lifebar before he depletes yours. CS is very similar in this aspect, besides not having all action centered into a single screen. I personally don't enjoy FPS games that much, so I wouldn't bother spending time on watching competitive games, but I'm pretty sure I would be able to follow CS more easily than I would with LoL or DOTA.
The reason not every FPS is an eSport is because not every FPS has an audience and a competitive scene. The ones you mention absolutely do though, CoD included.
This is where you make the mistake. You don't have to understand a game at the competitive level in order to watch it, and with an FPS people you can pretty much make an educated guess as to why they are camping in spot X or unwilling to just run into corridor Y. Even if you fail to make such guesses, you have commentators. Again, you don't even need to understand the skill of the players.
MOBAs however, to even understand them at a basic level you need to have played them. I played LoL until account level 10. I know what Annie is, but I have no idea what Tibbers is (I assume it's the bear?). I have no idea what the jungle buffs do. I don't know more than half of the items probably, I have zero clue about the meta and why certain characters are good. I actually don't know half of the characters. And this is coming from someone who has been gaming since I was young, and usually above average in whatever I played, and someone who actually touched LoL for a handful of games. Now imagine someone who never played games to begin with, MOBAs will just be an incomprehensible mess. Show them Street Fighter, CS or FIFA or whatever, and they can watch it. Hell, even Starcraft is more watchable for oblivious people than MOBAs imho.
The idea that someone who played a few LoL games vs bots will somehow understand more of the LCS than a random person understand of a competitive CS game is pretty ambiguous. They'll probably even get their asses handed to them by those bots if they never played games before.
Yet it is still an eSport, despite its blatantly obvious flaws. This is my whole point. There's a competitive scene, there's money involved, and there's an audience.
As mentioned above, I played LoL until account level 10 and am a seasoned gamer. I could probably watch LCS but I'd probably get no enjoyment from it since it's far too distanced for me since I won't grasp half of what's going on. I'm not even gonna imagine my sister who played nothing past Final Fantasy and Kingdom Hearts trying to watch that stuff. I can probably let her check CS though and even though the chance of her spotting ANY intricacy is probably zero, she can at least understand what's going on. Heroes of the Dorm was broadcasted on ESPN and there were a lot of tweets from people who said stuff along the lines of "I have no idea what's going on but I can't stop watching" and so on. MOBAs are just too convoluted to follow without actively playing them.
You need to actively play LoL to grasp those games. Without actively playing you won't understand what's going on and what the meta is about. Either way, no one is arguing against LoL being an eSport so I don't know why you bring it up. LoL did a great job at becoming and being an eSport. That does not mean that LoL is a benchmark for what games have to live up to in order to be considered an eSport. eSports existed before LoL did.