Dr. Doom's current goals..honestly, keep him from being able to go forward with world domination. 1 step at a time people, need to get pesky Reed Richards out of the way first.
 
~Jynx

Oh and it is very difficult to find good henchman these days, hard to rule something as big as the world if everyone who works for you is a lazy bum :p Better to use doombots 
 
~Jynx

Maybe. 

" Didn't Doom rule the world for a while, in 2099? :P  Maybe Doom would prefer the world to surrender and obey him... Taking it by force would cause civil wars, rebel factions, etc..  Though I would like a new Marvel Event to be centered around him someday.. (after Hulk events, a Skrull event, an Osborn one, a Doom would be great~) "

He already did it once. I don't remember when. It may have been in one of my Marvel Masterworks: Spider-Man collections, but he definitely did it.
 
EDIT: Basically, he took over the world, but was unsatisfied, since no one actually knew that he'd done it. So he freed magneto from his control, and allowed magneto to battle him for the world. Magneto managed to rally a good enough group, and saved the world from Doom. But if he'd really wanted to, Doom could have kept the world.

Of course he could. There's just many people ruining his plans.

" I think the answer to this problem has a couple parts to it, some already mentioned: 
 
 1.) Comics are really a parabolic way to discuss the internal and external struggles of good and evil and show that with enough effort, good will prevail in the end.  This overall message keeps writers from putting Doom or any other villain in the driver's seat as the evil world ruler. 
 
2.) Readers don't want to see this happen.  Much of comic reading is a vicarious experience; we readers like to feel as though our own problems are solved as Spider-Man bashes Doc Oc through a wall or Superman launches Darkseid into the void.  Imagine how we'd feel walking away if the bad guys always won.  Pretty icky, I think. 
 
3.) (Last one, I promise).  I think Doom is a bit more of  a complex character than you're giving him credit for.  He was Reed's friend and one of the original members of the Knight's of the Atomic round table.  He helped save the Fantastic Four and the world in Heroes Reunited story arc, and made numerous other efforts to preserve instead of to overcome and destroy.  He doesn't possess the unbridled evil of other characters; he simply serves his own agenda and does what he sees as best for himself and his country.  Getting global attention by global domination just doesn't meet his needs. "

" @ComicMan24:  
  

"

" You know. After the Big Live Live, "LIVE" show. I thought everyone would take the day off.  "

of course he can. He just doesn't want to.

World Domination is such a tired trope that even the Comic book world has avoided it altogether.

He can conquer, but not rule. He's clever but not wisdom.

Dude's overpowered. But I love the big lug anyway. :P

He could...If he's in the right mood.

I smell an event. HOUSE OF DOOM!!

He doesn't want the world, he just wants to crush Richards.... AND I SAY LET HIM ALL HAIL DOOM!

It's not like he hasn't tried recently, Was I the only one who read DoomWar. He came pretty damn close to winning at the end of the day and more improantly he ruin an entire country just to rule the world. Doom a pretty cold customer

" He could rule the world, but how will he fix healthcare? "

All shall bow before Doom.