I spent years not being able to get "that" guitar amp sound that I grew up with. Tried a bunch of modern valve amps and they all sounded nasty and fizzy to me, even used clean.
Decided it was down to how the old amps were built & that is when I figured out that all the old amps I liked in my youth were cathode biased.
So I built a wide panel deluxe clone & instantly had both the clean and slightly distorted sounds that I remembered.
Fast forward to amp sims.
Same deal, except the only ones I have found that get close are S-Gear and (amazingly) Peavey Revalver latest version.
I also own Waves GTR3, Amplitube 3/4 and Guitar Rig, among others, so irts not like I havent been trying.
Don`t get me wrong, the sims do not get 100% of the way there, but there again I havent managed to get a mic`ed real amp to sound exactly like it did in the room, either.
There is more to getting a great recorded guitar sound than "do I use a sim or a real amp?"