I think Activision had their prime time in the 80's when they released some really good titles for the Atari 2600 among other things. After that they became purely a publisher with no in-house development so staying loyal to Activision makes little sense to me given they no longer actually do any development. In fact they may always have been a publisher, it's just that in the 80's, giving credit to developers was actually very uncommon.
That's what made EA special in the 80's. They actually were the first publisher that straight up put the developers in the spotlight, releasing games in record style LP sleeves with artwork that highlighted the talented people behind the games. Which is a far cry from how they became in the late 90's and onwards with more and more focus on their branding, and up until now where their branding is all over the place and they've consumed developers and ruined franchises left and right.
So as for EA and Activision, both of them were at their best in the 80's and even early 90's. EA in particular released a lot of great titles for the Sega Mega Drive/Genesis with their signature "yellow button" cartridges.
Bethesda's prime time probably came around the 2000's when they released Elder Scrolls 3 Morrowind. Up until that point they had been kinda obscure. I at least had never heard of them until Morrowind released. They had a fairly good track record up until Fallout 76 all things considered. Fallout 4 got its fair share of criticism sure, but Fallout 76 is what I consider a big turning point for the company.