He wasn’t a vampire or a mummy or a werewolf or a ghost.
He was sort of a zombie but he doesn’t really fit that stereotype. Or maybe a robot but again it’s not a good fit.
He was a reanimated corpse.
But really he was a pioneering monster, defining his sub-genre, much like Dracula is the model from which all vampires take their lead.
In D&D he’s a flesh Golem, which actually works.
I’d call him a “construct”; but then I’m a Girl Genius fan.
Varney and Ruthven and Carmilla would argue that Dracula came late to the party.
In Danse Macabre, Stephen King said that Frankenstein’s monster is an archetypal “thing with no name”. That works for me.
It does depend on which version, but originally, he was man brought to life. He was intelligent and fully human emotionally, though originally more like a child than an adult. He mostly wanted to be left alone.
Once the movies came along, that characterization ended, and when anyone tried to revive it (e.g., Kenneth Branagh), people hated it*
*One of the stupidest pieces of criticism I’ve ever read was a review of the movie that asked “Why did they set the first scene on a boat in the Arctic?” Because, dummy, that’s how the book starts out.
There’s got to be some series or webcomic or something I follow that you don’t, or vice-versa.
Though “construct” would satisfy the D&D fans, too, since golems are an example of the “construct” creature type.
No, he wasn’t. It’s pretty clear that in Shelley’s original novel he wasn’t made by stitching corpses together. He was made from rendered-down materials, some of them not even from human beings, all re-assembled into a newly-created being by Victor Frankenstein. See my essay **The Worm or the Spaghetti?**in the first issue of the revived Teemings.
http://www.teemings.net/series_2/issue_01/worm_or_the_spaghetti.html
In RL he’s just a golem.
A classic Golem – made of solid clay and animated by the ineffable Name of God – Frankenstein wasn’t.
Something between a golem and a proto-android.
No indeed (and neither was his creature ;)).
Really, I think it’s doing Mary Shelley a disservice to try to equate her creature to anything from folklore. The classic Universal horror films put it in the same bag as Dracula and the Wolfman, but it doesn’t really belong. Shelley was quite explicit in her preface that she didn’t intend for there to be anything supernatural about it – it was created by man through science. Perhaps its closest precursor would be a homunculus?
In film history, the homunculus certainly is his predecessor. The six-part series was a hit in Germany, especially in Berlin, just like all the other movies about artificial creatures; they not just fit into the zeitgeist but also modernized well-known narrative subjects.
I make no apologies. The term “Frankenstein” has been used to refer to the creature since the dramatic adaptations of the 19th century, and is more commonly used for the Creature than his creator today.
I think there is a connection with the golem legend. In both cases it was men creating an unnatural form of life and then suffering the consequences of their hubris. The only update was that Shelley had the means of creation be pseudoscientific rather than pseudoreligious.
Frankenstein’s monster was a hybrid, like a Toyota with a stuck accelerator.
No apology expected. I intended the 
to indicate that it was a purely pro forma quibble in the usual SDMB spirit of petty pedantry. I appreciate that’s quite a load of meaning to expect a simple graphic device to bear, so if it wasn’t clear that’s my fault.
Second-hand
This is lovely and encapsulates so much, so well.