This is something I have been tossing around in my mind for awhile now.
On the topic of what game mode is going to be better for competitive play I have observed something with team vs team game modes that tap into addiction in ways that 1 v 1 cannot. There are actually a number of mechanisms at play when it comes to team vs team play that need some serious analysis and SHOULD NOT BE UNDERESTIMATED. You mention 1 v 1 being popular and I can agree to an extent, but when it comes to team vs team it is a lot more predatory in nature. Ranked 1 v 1 needs to exist not just because its a popular mode but as a way to provide players with some kind of out. Its actually a moral obligation.
Gambling is very addicting (Duh!):
Team vs Team, especially solo queue is a gamble. As in almost all aspects of this gambling are naturally addicting to play. Will I get a good team this time? Will the enemy team roll us? Maybe someone on the team is going to tilt or throw the match. Maybe the enemy team will get someone who leaves early. Then you provide the player with a bunch of options to further the gambling aspect more. Many different characters and builds to toy around with. All of which randomize the experience in some way.
You have others to blame:
The rest of your team are all fucking morons always. Nevermind the fact that higher ranked players tend to be people who will work with a Torb main rather than bitch them out in voice chat. The bottom line here is that YOU are special, YOU are the one who knows how its done. YOU are carrying the team. YOU are being awesome while everyone else farts around. YOU YOU YOU YOU YOU. If YOU win its because YOU are awesome. If YOU lose its because your team sucks.
Ok so I am making jokes right? Well, stop for a second and think about how this effects your brain. Think about addiction. Pay attention to this aspect. Basically you are given a free ride to be a total bad ass in your own mind. As long as you come back to the game you can be this super amazing player again. You do want to come back right? Of course you do! Now pick one of 20 plus characters and do your best to pull that slot machine lever.
Effective ranking systems perpetuate how awesome YOU are:
Overwatch is a great example of a game that tends to give you very even matches fairly often. You never get a chance to get sniped by a worlds leading player or see people carry their team in disgusting ways. Thus you get to stay on your throne and you are almost never thrown off it. Every game can be about YOU because you are almost never thinking about someone else.
In Quake/Reflex you tend to try and size up your opponent, you become worried if you are super out matched. Its actually a thought that goes through your head. But for most people who play something like Overwatch you probably wont even remember a single persons name. Only at high end play will you see people actually size each other up. At low end play you are always a rock star.
You are encouraged to keep others playing:
Since its team based and you "Got unlucky with Solo Queue again" you might decide to team up with some friends. You decide you want to make a team! YAY lets now take everything I said above and toss tribalism into the mix. Again, I stress that you pay attention to how this effects the brain. Tribalism is a huge brain effecting topic by itself.
The ranking system is a slot machine at low level play, but is a ranking system at high level play.
At high level play, you managed to get there by doing something right. In this case its working for you. In other words the vast majority of the player base might as well be in a gambling casino. Its super effective on both fronts. It appeases the masters of the game while it drugs up the casuals with happy pills. (uppers and Downers) Its fucking insane how well this actually works. Its a single feature that effectively hits pros and casuals in different but highly effective ways. Not only that but it gives credence to the value of each rank point thus making the effect of getting more points more potent. Its an entire self sustaining microcosm of addicting aspects that feed into themselves. Just think about that.
In 1 v 1 there are almost no gambling aspects involved, its very cut and dry.
You either win or you lose. This mode when done well is basically a bucket of mother fucking cold water. I cannot stress this enough. with the above points you can become entrapped into a mind boggling alternate universe where you are a super snow flake and the entire rest of the world is holding you back. This aspect effects everyone to different degrees. MOST people feel they deserve a higher rating than what they are in competitive, once this happens it hits nearly every key aspect of the human brain to remove blame from yourself, gambling and countless other things. Its drugs, its more than a simple dopamine dispensary. Its a gambit of addicting aspects.
This is not a small thing, if you pay attention to how the human brain works. team vs team is even more predatory than gambling casinos. It hits almost every aspect of the human brain in one foul swoop. I am even willing to describe it as being insidious. Not that I am against it, but until I really took it apart I didn't know why I was playing Overwatch for insane amounts of time but could only make time for Reflex or UT4.
Reflex and UT4 only offer cold water bucket splashes.
It offers very little in terms of dopamine or reward. The type of enjoyment I get from Reflex and UT4 are innocent in nature. Its a "simple" experience. Loading up Overwatch is like doing a line of coke. Oh god that analogy is way too accurate ><
Game devs are getting better at their jobs, we are now stacking addicting aspects into more feature robust designs.
I am almost convinced that if you can get a solid team vs team mode in reflex or ut4 that effectively hits the brain in all the right places popularity would sky rocket. It wont be as much as Overwatch but it will be a lot more than it is now.