Modern MBTs (or even WW2 MBTs) are far from being unstoppable. Any proper artillery round or airbomb coming directly on top and it's the end, any good AT rocket (RPG-29 Vampir, Eryx, etc) and that's over, any good ATGM, and that's over...
I heard recently that the survival probability for infantry in a theorical symmetrical all raging battle these days is a lot higher than the one for a tank crew.
Not strictly true, some MBTs are pretty durable, Merkeva and Challenger 2 particularly. I recall stories of Challenger 2s shrugging off multiple AT rockets, but I'm not sure about a bombing from the air or heavy artillery.
A main battle tank is pretty much immune to anything ground forces can bring to bear except a HEAT round. The problem with tank armor for most weapons is that it's all ablative, layers of ceramic armor and dense metal. Especially in the glacis plate, it's essentially impenetrable. For all intents and purposes, a main battle tank on the ground is not feasible to destroy.
For a while, the idea was just to blow a hole in it, but that hasn't been possible for a while. Then, someone got the bright idea to launch a concussive weapon that would simply send a shockwave through the cabin and kill everyone in it. That worked until they started layering in the ceramics. Now, the only way to really effectively destroy a tank is to use a penetrator round to throw shrapnel around the inside. That takes a pretty serious piece of ordinance. In terms of Gen 3 main battle tanks, that's not going to be potable.
Tanks can be destroyed, but they do have ground superiority. About the only things infantry or anyone else can hope to do to a main battle tank is to somehow break the treads (which is a LOT harder than it looks).
However, you might be right in the case of a symmetrical battle, Lyn, because being the big dog on the field means you're the first to get a bullet. If we assumed two well-equipped nations went to blows with every conventional weapon they had, the infantry would probably survive better simply because there are usually more of them to target. If you're in a tank on a modern battlefield, you're a target. While no recent wars have seen a battle of that nature lately (right now, an M1 crew is essentially untouchable by the Taliban since the old explosives-under-the-tank-where-the-armor-is-weak doesn't work anymore) ground superiority doesn't mean total battlefield superiority.
It's actually some spectacularly old-fashioned aircraft that I'd say constitute the most frightening nightmare for a tank crew. The A-10 Thunderbolt is a predatory reptile of an aircraft, a new evolution of a prehistoric design. They just built a plane around the most massive gun they could make. It'll put 30mm rounds completely through buildings and pulverize the foundation until it collapses. I've also heard it can go through the armor on an M1 depending on the range.