Contracts require four elements in order to be valid: offer, acceptance, consideration, and intention to create legal relations. EULAs fail at multiple of these:

1. As I already said, they offer no "consideration" because you already have the right to do the thing they purport to give you permission to do (i.e., make the incidental copy necessary to run the game).
2. They lack "acceptance" and "intent" because they are contracts of adhesion (sprung on you after the sale transaction is complete and you already own the copy of the software), and clicking through them is nothing but a mechanical act necessary to use your property (which, again, you already have the right to do, by definition of "property!") with no legal intent behind it. And if you have no intent, how the fuck can merely doing a thing you're being forced to do constitute "acceptance?" It is, simply, complete bullshit.

If it were presented at the time of sale and you had to agree before the money was exchanged maybe it'd be different, but that's not how they do things. And even then, it would still fail at "consideration" unless they offer you something above and beyond the right to use your property, which I cannot emphasize enough, you already have.

(By the way, since it sometimes comes up as a "gotcha" rebuttal attempt: no, Free Software licenses are not EULAs, and that's why they are valid while EULAs are not. You are not required to "agree" to the GPL etc. merely to use the software; it only kicks in when you want to do something, like modification or redistribution, that would otherwise be copyright infringement. It grants you those new privileges in exchange for accepting its terms, and that consideration is what makes it valid.)