I'm not even going to show you the new one first. First, I want you to look at the one that started it all, and sold a million Xbox 360s:
The Mad World trailer is a classic for good reason. It says nothing about the plot, and everything about (1) the feel and (2) the spectacular other-ness that Gears brought to the table. It shows us so much about the world and instantly makes us care about whether or not Do-Rag McGee will make it out of this one.
Then, we have Gears 4's trailer.
Do-Rag McGee had a kid, and that kid is running from... something? Through the woods? And there's a creepy black monster after him but nothing approaches the actual world-building and exceptional design of the Mad World trailer.
Disappointed. I'm always a little hyped for Gears trailers but I give this one one pinkie up. That's as close to a thumb as I can muster.