I recently went to EPCOT for a day solely with the intent of riding Cosmic Rewind all day. Ended up getting 8 rides on it and the pre-show truly ticked me off by the third time around. Its just so ridiculously long, the acting is horrible from everyone (except Bautista, he's actually doing a petty good job as Drax), and the guests in there are the absolute worst. Marathoning Cosmic Rewind and having to wait an hour long line every time really isn't too bad for me, its the pre-show that truly takes a toll on me every single time.
Compare this to the many times I've marathoned Mission: Breakout. I tend to usually get 20 rides on Mission: Breakout when I do full day marathons on it and out of the hundreds of times I've ridden it, I've never found the pre-show annoying. I actually enjoy watching it. Its quick, it's pretty cool thanks to the matched energy between the screen and the physical environment/Rocket animatronic, to the point, and the people are (usually) not mobbing the exit door like on Cosmic.
It honestly makes me wonder just how different that original pre-show on Cosmic Rewind would have been if they kept the Rocket and Groot animatronics and (physical?) Milano ship in the background.