While I agree that skill and strength certainly plays a part in a person's ability to precisely decapitate another person, it is made to look way to easy in Hollywood.
Depends on the weapon and whether the good guy was a dwarf. Everyone knows dorfs > all in a scrap.
A friend of mine used to explain the Hobbit's progression through the movies from the Middle Earth RPG perspective. In that game you receive exp for doing everything for the first time (opening a door, riding a horse, swinging a sword) so after their massive journey, meeting Elves, Men, Dwarves, Nasghul, etc they were heroes in their own right. Even seeing a Balrog would be enough to kill a low-level mortal outright. The dwarves inside Erebor were all heroes and as such would have been significantly more powerful than your average warrior so portraying them as lopping off the heads of orc footsoldiers would be perfectly acceptable within the canon of the storyline.
As a guide, here are the levels of some LOTR people taken from
"Lords of Middle Earth" (MERP):
Balrog: lvl 36 - Maia Fire Spirit.
Gandalf: lvl 40 - Maia (Istar), Mage/Magician, "Gandalf the Grey".
Gandalf: lvl 50 - Maia (Istar), "Gandalf the White".
Saruman: lvl 50 - Maia (Istar), Mage/Alchemist, "The White Wizard".
Arwen: lvl 15 - Half-elf Bard, daughter of Elrond, wife of Aragorn.
Elrond: lvl 65 - Half-elf Animist/Cleric (Bard, Lay Healer, Fighter) of Imladris.
Galadriel: lvl 60 - Noldo Bard/Mystic (Seer), Queen of Lorien.
Legolas: lvl 8 - Sinda Warrior/Fighter, a young Legolas around T.A. 1640.
Legolas: lvl 28 - Sinda Warrior/Fighter, at the time of LOTR.
Aragorn II: lvl 27 - Dunedain Ranger, Member of the Fellowship.
Aragorn II: lvl 36 - Dunedain Ranger, as King Elessar.
Boromir: lvl 20 - Dunedain Warrior/Fighter, Member of the Fellowship.
Faramir: lvl 24 - Dunedain Ranger, married Eowyn.
Theoden: lvl 24 - Rohir Warrior, 17th King of Rohan.
Nazguls: lvl 32-60.
Bilbo Baggins: lvl 9 - Hobbit Scout/Thief, Ring-Bearer.
Frodo Baggins: lvl 12 - Hobbit Scout/Rogue, Ring-Bearer.
Peregrin Took (Pippin): lvl 8 - Hobbit Warrior/Fighter.
Samwise Gamgee: lvl 9 - Hobbit Scout/Thief, Ring-Bearer.
Gimli: lvl 8 - Dwarf Warrior/Fighter, Member of the Fellowship.
Gimli: lvl 21 - Dwarf Warrior/Fighter, "Elf-Friend", Lord of Aglarond
Smaug, while not on the list weighs in as a level 66 named dragon.