Not really. Yes, Halo majorly popularized online mp on consoles, but it didn't invent it. There were some others that were ahead of Halo, mainly on Dreamcast, but we all know how long that life cycle went. With that said, there are plenty of FPS games that made multiplayer popular or added more awareness. Goldeneye, Doom, Quake I & III, Unreal Tournament, etc.
Where @Fallen Soldier's anger is coming from is the sin and the wrong direction a lot of the industry took during the 7th generation and now with the Battle Royale modes. That if your game does not have competitive multiplayer, it won't sell or is doomed to fail. The funny thing is, most games that tried to copy Halo, Gears of War, or COD4 all failed to captivate, and a majority of them have been forgotten about, or are a very small footnote in history. Never getting to the next generation. That same sin is being seen in this industry and certain streamers on Twitch who are all about BR and nothing else. To an extent that they (falsely) believe that if Halo: Infinite does not have a BR mode, that won't survive. Infinite does not need a BR mode to be good nor survive, you selfish dick-wads want it that way, because you're afraid you won't get the maximum view count you desire. If Halo added a BR mode, it was just be another clone in the crowd, and you guys and gals would play it for two weeks at best, and drop it and get bored. Going back to Fortnite, War Zone, or PUBG. To the extent that one Twitch streamer, called The Doc, kept talking about how he wants a BR mode, while looking at gameplay demonstration of the single-player, and felt all assets were wasted. For the single player! You're part of what's wrong with the gaming industry you assholes!
I did specify it only popularized mp on consoles, but never implied it invented it there. Goldeneye was earlier but only couch mp. It’s the network mp and death match focus that blew up on consoles with Halo and yes, started some of the industry’s longest lasting and worst trends, leading also to some of the worst industry practices.