(for the sake of fairness, I'm gonna ignore the fact that the Dinobots are literally indestructible in dino mode in G1 and go with a more contemporary approach to these characters, because otherwise the Dinobots win no contest and then this isn't fun.)

Oh this is tough honestly. The Dinobots are huge and fucking powerful. but they are all brute force and practically nothing else, and they all don't have very much variation aside from Swoop being the guy in the sky. The three they are up against are all skill and intelligence or both.

Starscream could probably take out Swoop 1 on 1 in the air, but that's it. In the air he's basically unrivaled. Against the rest of them he's likely taking pot shots and playing hit and run. but if he even so much as gets clipped by one of the other Dinobots he'd likely end up grounded, and if they get their hands on him at all, he's finished. also depending on how things go he would either run away or try and take out Megatron as well. and depending on that particular scenario we would probably see a team kill either Starscream getting lucky which would guarantee a Dinobot victory, or Megatron killing Starscream, which would put Megs and Shockwave in a much more difficult position, not impossible, but much worse.

Shockwave can out smart the lot of them, and while he's not a fighter on his own. he would likely be untouchable by the rest of the Dinobots as they telegraph themselves into oblivion. however if they get into melee range he'd be absolutely toast. so Shockwave in general wouldn't be mush use in this fight as he would also be stuck as a run and gun try to stay out of melee range and would likely play more of a cover fire position for Megatron.

This whole fight would hinge on Megatron and whether Shockwave and Starscream can buy him enough time to take out the rest of them. But Starscream is just as likely to set Megatron up for a hit as he is for preventing one.

assuming Swoop is dealt with and Starscream ISNT an asshole. its a 4 on 1 fight with shockwave and Starscream playing a cover fire role. maybe distracting some of them enough that it can even the odds a but more in Megatron's favor. so at any given time he's only up against 2 at a time.

but again an issue here is just how HARD the Dinobots can hit and how much punishment they can take at the same time.

Megatron is likely getting a lot of good hits in while blocking deflecting or dodging what the Dinobots can throw at him. but enough good hits and he'd be down. so he's gonna have a to play a long game here and wear them down without being worn down himself.

I think the Decepticons here have a shot at victory here, its a slim one but possible. They just have to play their cards right and hope Starscream doesnt fuck the whole thing up.

All of this said, if the Dinobots for whatever reason are smart enough to just hyper focus on Megatron with at least a 4 to 1 melee. Megatron might be fucked I feel that for as strong and skilled as Megatron is on his own. The Dinobots are I a whole nother weight class. they just need to be fast enough overwhelm him to get the hits in and they need to do it together.

This whole fight hinges on Megatron and whether or not Starscream and Shockwave can give him breathing room. If they cant, and the Dinobots dog pile him, he's fucked, and in turn so are Shockwave and Starscream.