Regardless of what word best describes Andy Murray's historical status, this debate just furthers the point that he not only has held an interesting position during this era, but also historically...has he been the "worst of the best" or the "best of the rest?" Is he the least of the greats or is he more the best of the non-greats? That depends upon how you want to look at it; I think both are true.
The most comparable player to him, in terms of historical ranking, is Guillermo Vilas, who was especially dominant on clay, won 4 Slams and 62 titles and is undoubtedly the greatest player never to rank #1 (although there is some controversy about 1977, when he won 16 titles and 2 Slams but finished #2 behind Connors, who didn't win any Slams and only 8 titles, but reached two Slam finals and won both the ATP and WCT finals, whil most of Vilas' titles were very low level). Vilas was generally overshadowed by Connors, Borg, McEnroe, and Lendl - but he was always there, in the mix, with year-end rankings of #6 or better from 1974-82.
Jim Courier is another comp, but he had a rather different career: more of a higher, but far shorter peak, but overall a weaker resume. He's more similar to Lleyton Hewitt. Ilie Nastase and Arthur Ashe are also comparable, but lesser to Murray in terms of career records.
Above Murray you have the cadre of "lesser greats" like John Newcombe, Mats Wilander, Stefan Edberg and Boris Becker. If you get past Slam count, Andy's overall career is close to these guys. In fact, if you replace "Slam titles" to "Slam finals," Andy's career is better than Wilander's. Now Andy did only win 3 Slams to their 6-7, so in the end probably has to be ranked lower, but it is far closer than Slam titles would entail.
In the end, I'd probably put rank Murray right between Wilander and Vilas on the Open Era list. I think it is clear that he's one of the 20 greatest players of the last 50 years, although not one of the 10. Is that "special?" I'd say yes. But specialness isn't either or; it is a matter of degree. The only way we can really say he's "nothing special" is if our definition of "special" is Federer, Nadal, and Djokovic, but then we're left saying that Pete Sampras and Bjorn Borg were "kind of special."
I can be sloppy with the details, but I think you get me on the big points. (I didn't watch tennis at all in the 80s and 90s, so there's a whole raft of players that blur together for me.) Not Vilas...I loved him. But Wilander...he's just a name to me.