Mark Bagley from his run on Amazing Spider-Man.

Ditko is certainly unique. I don't remember ever anyone aping his style.

I wish I could reconstruct the whole development of my learning to recognize art styles. I remember being indiscriminate the first few months, but developing some tastes as my collecting accelerated.
Kirby was most likely the first; it was one of his comics that started me in comics in 1971. From a current perspective, it's hard to conceive of not being able to recognize Kirby, but there at my start, he had some easy-to-spot giveaways that didn't require any art-spotting abilities,specifically, three splash pages dividing the story into chapters, one two-page splash. I remember at the time thinking Kirby's books were cheating me out of story content, especially since so many of the multi-panel pages only had four panels. So even if the art had been blacked out, you could still recognize Kirby by the structure.
Aparo was probably next, since I was so fascinated by B&B that I pored over his pages intensely. He was my first "favorite" artist.
Using Mike's Amazing World of Comics newstand to recreate my path, the next artists to have enough impact for me to learn their styles were probably Sal Buscema, Gil Kane, Neal Adams, and Herb Trimpe (I specifically remember recognizing his style when I saw it on the TV cartoon ads for Crest toothpaste). 
By the time I could recognize Wrightson's style in Swamp Thing #1, I was at the one year mark, and I probably had a good grasp of the most prominent pencilers at Marvel and DC, but I was nowhere near being able to identify inkers yet. 

Yeah, I have to agree; Milgrom and Frenz (not sure about Pollard, seems to me like he was influenced far more by Kirby and John Buscema, if anyone), as well as Starlin and Byrne, were certainly influenced by Ditko, but I wouldn't say they ever aped his style outright - I think Starlin came the closest, but only in certain panels of his original Warlock saga.