Comprehensive within the field of philosophy? Yeah, I think that can be achieved. Wikipedia articles on core philosophical articles are often not much more than stubs - certainly the SEP examples seem more coherent and well structured. I don't think there will be more than 1500 articles better than C-class in Wikipedia's Philosophy category.
SEP articles are definitely better-structured, especially the ones on general overview subjects. I think that's a general property of the respective authoring models. Wikipedia is good at specific articles on well-defined subjects, while the general overview articles often range from incomplete to haphazard. An encyclopedia written by individual expert authors is better at crafting long overviews, which often require subjective and carefully curated synthesis of material.
But I use them both, for different things. The general overview articles are much better at SEP than Wikipedia. But Wikipedia has a lot more narrow articles, on subjects that SEP doesn't cover at all, or mentions only in passing in one paragraph of an article. For example, a huge number of short-to-medium-length biographies of historically important philosophers (SEP instead has a small number of quite lengthy biographies).
I do wish something like SEP existed in more other fields. I don't know of anything like it for computer science, for example.
Sometimes I find Wikipedia's "haphazard" articles are actually a benefit, because in practice they often seem to end up covering a subject from multiple angles, with lots of examples etc.
My impression is that in many cases this is because there were multiple major authors without a master plan for writing the article, so they ended up sort of putting it all in.
For someone (like me!) who's struggling to grasp a subject, seeing a subject described from multiple points of views, targeting varying levels of expertise, can be immensely helpful.
A traditional encyclopedia article, on the other hand, is probably more likely to be well-structured and comprehensive, but ... I think can be harder to grasp for someone that's not quite up to the material.
It may be kind of ugly, but the "Just throw it all in!" approach does have some real merit...
