Power has always been Doom's narcotic of choice. And he didn't stop at the Silver Surfer. He once stole the powers of a Watcher (Aron the Rogue Watcher that is) and some creature from space called "The Hunger" in FF#381, which lead to his "death" in FF#381. Also, in the imagined events in the mini-series tribute "The World's Greatest Comic Magazine", he even ended up stealing Galactus's powers by using various power objects like the Cosmic Cube and Annilihus's Power Rod. More recently, he downloaded the Franklin's reality engine that powered the Heroes Reborn planet and was able to bend reality to conform to his wishes.
You don't get the essence of it from the film, but having been raised in Latveria as part of the disenfranchised gypsy population, his tribe was always under the thumb of the ruling class. His thirst for power stems from that.