Guitar sound

Why is it that my guitar doesn't sound the same recorded as it does live in the room??
Live my Marshall sounds pretty classic marshall with a nice sustain that will slowly turn into controled feedback.But on tape the amp sounds really dry and flat and blah and a lil weak like its lacking gain.
Tonight I was just layin down Idea's in the studio.My amp alone into the board sounded like a cardboard box.I fiddled with a parametric EQ in the channel insert and it helped a lil(didn't spend much time).The only time the amp sounded professional was when the delay was added at the board(seemed to not sound dry),but I don't need echo on everything,ya know.
My amp was miced with a 57 into a mic pre into the board.I tryed a Sans amp direct into the baord it was too buzzy for my tastes but seemed to sound way more(for lack of a better word)Hi-Fi than my amp.
I never really done much studio stuff.Is it that my amp sounds that dry in person and I'm a deaf basterd or is it recording techniques that get that sound??I know live I get allot on comments on my tone.
Any insite is welcome thanX

Allright another way of asking is:Is proffesional recorded guitar tone as simple as mic it up and play or is there EQing and stuff added at the board to make it not sound dry.
Basically for example Angus Young runs a JTM45 in the studio and you don't hear effects on the record,yet the amp doesn't sound dry and flat.Hows that done?Basically it don't sound like a dry amp in a dead room.
i think the "lack of gain sound"I'm describing is that its so dry that I'm hearing every nuance of my fingering and pick attack,that I don't normaly hear in the room.
Why does the Sansamp(besides buzzyness)sound more like a professional recorded tone that the Marshall??Is it cause its direct and has a amp simultor DI or something so it don't need board doctoring?
I really don't have a clue here,every time I've done a recording has been a local studio thing and allways hated my guitar sound.