One thing i like abt doomguy is hes simultaneously his own character, with deep rich backstory and personality, but also like. he can sort of function as a quasi-power fantasy self insert for the player. Sort of like Link or Gordon Freeman. You put yourself in his shoes, and experience the universe of DOOM through him. And in a way, I think that, putting aside the run 'n gun shooty tooty nature of the series as a whole, it actually offers meaningful immersion in a way.
i have a problem with third person games where i just can't get as easily invested in the characters i'm meant to play as. It makes it more difficult for me to do what the game aims for me to do in that scenario.
i have a far easier time experiencing things in a first person perspective, although there are cases where i like the third person or isometric views. and i feel there are a few instances where a first person perspective isnt as immersive as it could be.
Then again, every dev or dev group has their own ideas for how they want gamers to play their games! i wonder how different DOOM would be if every game were from a perspective similar to resident evil, that being a third person over the shoulder view. what would games like dragon age be like if they were entirely first person perspectives?
... Anyway, that aside. I love Doomguy. He is an incredible guy, and I think hes one of the most interesting characters ever to be made. I also want to say that, hes very fun to play as too. The action in every DOOM game is great, even if it takes a while to get used to the fast pace and how complicated combat can get. Amplified by the tools at your disposal, you have a variety of options in approaching combat. And it never feels stale either.