so what separates "major" tournaments from "minor" tournaments anyway? number of participants, venue of choice, sponsors, explicit blessing from developers/publishers via being part of the competitive league route, etc.??
It's mostly based around the attendance and generally the vibes as a result of that, but it's more than just strictly numbers.
Attendance
This has three major pieces.
- Number of attendees: Self-explanatory, I believe; the more folks, the bigger the event.
- Location variety: While there might be some high numbers, it might not considered as highly if it's heavily only folks from the area. Alternatively, some events can be considered beyond its numbers if it attracts players from a variety of locations, especially out-of-country.
- Skill: Of course, if you attract some of the best players there's a bit of a "validation." More than just "attracting one or two best players" too, especially it's just those folks stomping out all the competition.
Vibes
This is hard to explain, but there's just a specific feeling you get when you're there or when you're watching.
I've attended smaller, more cozy tournaments that gives the feeling of excitement every step of the event. As long as you're happy to be there for every waking hour you have and have enough variety throughout. (e.g. Michigan Masters [Rest in Peace])
I've attended large, scaled up tournaments for a lot of people just lack that wow factor, no matter how much money, space, hype, or sponsors are thrown at it. (e.g. Colorado Cutthroat Tournament + SuperCon [Rest in Piss]).
Other
Jut addressing other aspects you mentioned, venue of choice, sponsors, explicit blessing from developers/publishers, being part of the competitive league route, etc., are generally more of a result of marketed attendance.
Venues have been in great areas but less always accessible by more folks. Such as the ones taking place in the Caribbean or Japan even.
Sponsors will follow attendees, but also sponsor events that make their event seemed bigger with all the other event information and isn't always a good fit or reaches many folks. Same with Developers/Publishers (but usually are on far more "legit" tournaments).
Competitive leagues usually have attendance requirements before they sign on, or scale down the value of the tournament's points depending on the attendance.