A little late to the game -- but I'd like to come in and point out some of the things we'd lose if we lost Bay. They're pretty big things for me -- and things I think would be REALLY bad for the series.
1) MILITARY HARDWARE.
Michael Bay has an INCREDIBLE relationship with the American military. Whatever else you might say about him, he loves the American military and they love him. Good *GOD* the Transformers movies have benefited from this.
Take a look at other contemporary movies with lots of hardware. So much CGI, often UGLY-arse CGI. Hulk, and IRon Man both had to use CGI versions of vehicles that Bay got FOR REAL in both movies. Transformers is SO MUCH about the hardware, you GOTTA appreciate that Bay actually gets that hardware up on screen for us.
2) HE KNOWS HOW TO FILM A CAR.
Bay knows how light should reflect on a car. His influence on the special effects simply can't be denied. The wonderfully realistic look REEKS of Bay's influence -- the way the light sits PERFECTLY on the car parts even when they're moving. That is Bay.
Bay *LOVES* cars and military hardware and vehicles and he KNOWS how to film them. I wish he'd slow his camera down a bit, but still... it would be sad to lose his eye for cars.
3) BAY BELIEVES TRANSFORMERS SHOULD HAVE A SENSE OF HUMOUR.
I don't AGREE with Bay's sense of humour all the time. I think he went far too crass in the second movie with certain bits and pieces... but god damn it's a relief that he lets you have laughs while you're watching your giant robots. There's so many fanboy films with NO SENSE OF HUMOUR AT ALL. Take a look at Terminator IV, or X-men 3, or Wolverine, or... hell even the SPIDERMAN TRILOGY. They're so lacking in a sense of fun humour that when they DO make jokes it's kinda jarring.
The fact is that Transformers is absurd -- and Bay sorta revels in that.
4) BAY LIKES TO DO THINGS FOR REAL INSTEAD OF JUST USING CGI.
Sure there, is a LOT of CGI in Transformers... but... in the first movie BAY ACTUALLY BLEW UP A BUS. Any other director would have just made the entire Bonecrusher sequence CGI and it would have SUCKED. BAY ACTUALLY BLEW UP A BUS.
I cannot repeat that often enough. MICHAEL BAY ACTUALLY BLEW UP A GODDAMN BUS.
5) COLOUR.
It's funny -- the Transformers toyline for the movie looks so bleakly MONOTONE compared to other TF toylines... not so the movie.
Modern blockbusters LOVE colour correction, large, important films will colour-correct the HELL out of things. One of my BIGGEST complaints about the Lord of the Rings films was that they were SO DAMNED GREY. There wasn't the rich sense of a COLOUR FILLED world like you got from the books. The new Terminator film, the Batman films, the X-men films. So many movies sapped of all colour.
A different director might have made all the TFs stock grey and shot nearly everything at night to hide the CGI effects. Bay didn't. Bay EMBRACED the colour -- the environments are colourful, the characters are colourful, the whole movie is ALIVE and VIBRANT with colour.
Could you imagine how bleak Transformers could be done by Peter Jackson in his horribly monochrome Lord of the Rings style? Eeeeeyuck.
--Jhiaxus
(Don't get me wrong -- I think that Revenge of the Fallen was deeply flawed, but you know what? A lot of the things I *LOVED* About it were only there BECAUSE we had Bay as a director.)
(BAY ACTUALLY BLEW UP A GODDAMN BUS.)