<< How tall are goblins?
Orcs?
Elves?
Maiar? >>
Well Orcs are described as short/squat...height ranging from about 5'2" to 5'7" I'd say.
The Uruk-hai (the one's that Saruman bred in the movie) were taller though...maybe closer to 7 feet.
Elves are tall...6'2" and possibly higher
Maiar? Um..that ranges. Sauron and the Balrogs were Maiar but seduced by Melkor and turned evil and they now range quite a bit in their physical forms. Gandalf and Saruman are also supposedly Maiar...but it's just their spirits in the bodies of old men. Think of Maiar as more like spirits instead of being physical. If you are just referring to wizards...then just the height of Men I'd guess.
<< Where orcs "created?" >>
Early in the first age Melkor (the Dark Lord before Sauron) captured Elves and tortured and corrupted them. Then once they were corrupted/mutiliated they were just bred as a mockery of the Elves...which means they also don't die natural deaths like Elves. They are considered fierce warriors but of course they're no match for some warriors like the best Men and Elves...but in the great battles, Men and Elves also lost many people...not just Orcs. They are portrayed weaker than they really are in the movie. Don't get me wrong...Gimli, Legolas, Aragorn, and Boromir can lay waste to dozens of them at a time but don't assume the average Man or Dwarf could do the same.
<< Were the orc lords and goblin lords taller? >>
Goblin is basically another word for the Orcs....and what "orc lord" do you mean?
<< In the movie, what sort of creature was the big tall creature that lead the orc party which kindnapped Pippin and Merry? orc? Goblin?
>>
Uruk-hai (half orc, half man)...his name was Lurtz