It seems to me that Coleridge is a major poet. That probably doesn't look like a very radical thing to claim, but it is, I think, harder than it might otherwise be to ground. In the introduction to his 1966 anthology, 19th-Century British Minor Poets, Auden proposed four tests for being a ‘major poet’: write a lot; show a wide range of subject matter; exhibit an originality of style and vision; and manifest a style and vision that mature over the course of a career. Of those four, Coleridge is really only described accurately by the third. He did write a lot, but by bulk the overwhelming majority of his output is either derivative, manifestly minor, or else unfinished flotsam and jetsam, oddments and doodles and fragments. His choice of subject matter was not wide, and we can only talk of his style ‘maturing’ if basically giving up writing finished verse counts as maturing. I'm only speaking for myself, of course, but STC's poetic oeuvre divides into a large tranche of stuff I'd be happy discarding, a smaller tranche of stuff that's interesting, or suggestive, or worth persevering with—as opposed to actually good—and a thin sliver of output that stands with the best poetry I have read, in any language. A couple of the Conversation poems, and some shorter pieces for which I have deep affection, are inarguably very good writing. I know it speaks profoundly to some, but I've always had a take-it-or-leave-it relationship with Christabel, though it certainly has its moments. But Ancient Mariner is a masterpiece by any standard, and ‘Kubla Khan’ is simply one of the greatest short poems ever written. Tom Stoppard once said that when he read Eliot's ‘Prufrock’ he felt as he imagined the diabetic patient did as the insulin went in. ‘Kubla Khan’ has that effect on me. It's as close to flawless as any poem I know.
I once had a conversation with a friend of mine, who happens to be a Professor of Drama, about the relative merits of Shaw and Wilde. I suggested that Shaw was the better playwright, because he wrote so widely, and did so many interesting things with the form of the play. My friend pooh-poohed me: Shaw was good, he said, but Wilde wrote The Importance of Being Earnest, and that, he said, is perfect. But isn't that, I countered, like saying that The La's are a better band than The Beatles because ‘There She Goes’ is so perfect a pop song? He wasn't convinced. And now I find myself arguing the counter case. Am I really justified in claiming Coleridge as a major poet on the strength of a few really good, one great longer and one perfect short poem?