Fassy is hardly a "big" actor yet. And Hardy is just now getting there.
I was about to say that Craig was a big actor when he became Bond but then I realized he's big because of Bond.
Two of those movies have yet to be released and one isn't even in production. I still don't really think Hardy is a "big" actor, even though he was Bane. He obviously wasn't recognizable in the role, which hinders his fame a little, I guess you could say.
Fassy is hardly a "big" actor yet.
Now wait a second! Let's debate this for a second. Fassy is clearly a big actor at this point. He is getting offered tons of great stuff and is the lead in one franchise and is potentially about to have another one with Assassin's Creed.
I think this really depends on your definition of a "big" actor. To me, I basically equate it with being a household name. Fassy is far from that at the moment obviously, considering his biggest role was Magneto and a majority of people still wouldn't even know his name. Like I said earlier, Hardy is getting there, especially with all his upcoming roles.
The average individual has no clue who Michael Fassbender is. Tom Hardy on the other hand, is far more popular because of Bane and I wouldn't even call him a 'big' actor. They're A-listers in the industry, but they're not publicly known to an exceptional degree.
I also want to note I'm thrilled Mendes is probably taking on these next two Bond films, namely because, as I've said previously, it will offer some consistency in tone and vision unprecedented to the franchise perhaps beyond Dr. No to From Russia With Love. Mendes will be both more comfortable and confident with action and handling the film, but I hope it's a challenging enough direction it inspires the brilliance we all saw with Skyfall.