Actually I think Schwarzenegger could've made it in pretty much any time period. He practically created the very mold you're speaking of. Before him action stars were skinny and old dudes like Clint Eastwood and Charles Bronson, not very physically imposing but they always ran around with big guns. There was also Bruce Lee but again, he was like 5'7 and 130 pounds.
Now we're looking at the industry that Schwarzenegger practically created, with every studio looking for their own version of Arnold. But none could quite match the charisma that Arnold had, and charisma is probably a good 85-90% of acting to be honest (let's face it, Nicholson could get away with just playing himself in at least half the roles he's done cuz everybody simply likes his personality). The problem with the Rock is he has no personality. Watch Arnold in Pumping Iron, before he was "an actor".. dripping with personality.
The Rock actually reminds me more of guys like Seagal and Van Damme, never at the top tier like Arnold was cuz they simply don't have that extra thing going for them, whatever that extra thing is that makes A-list movie stars happen.
I just can't believe Dwayne doesn't have a personality. The man helped make pro wrestling achieve it's greatest heights with his personality. And he wasn't even one note with it, he changed it up throughout the years. He is practically one of the reasons WWE is a household name, with respects to Stone Cold that is. He can STILL captivate a live crowd of 100 thousand, something regular actors might struggle with.
Party Tip: when mom gives you Cheerios, drink the milk too! It's a balanced breakfast and good for strong bones! PARTY!