Your question is very subjective, but I think there are two ways to look at it:
Building a working space plane is pretty exceptional.
There's really nothing it did that wasn't done by something else.
The NASA shuttle was flown in fully-automatic mode for launch, and most of reentry. It's also the vehicle which pioneered the thermal tiles, the reentry profile of a space plane, and the general concept of a shuttle. Buran could almost be thought of as an iteration on that design. The Soviets used some lessons learned and, in some respects, built a better shuttle. Does that in itself make the Buran exceptional? Probably not.
The only thing Buran really did that the NASA shuttle never did was fly unmanned, including an automatic landing. That seems to be at the heart of what you're asking, so I'll address that specifically.
Autoland had existed for decades before Buran, so it certainly wasn't the first airplane to land on autopilot. Although, it may have been the fastest autolanding to date, which could be an argument for exceptional.
I would note that even though there was only one orbital flight of Buran, there were atmospheric tests of prototype vehicles (some prototypes had jet engines), so there were opportunities to safely test the autopilot during the landing phase of flight prior to the orbital test. In fact, it would have been the only phase of the autopilot that saw real-world testing prior to launch. So once Buran got on approach, the fact that landed safely probably shouldn't be too much of a surprise.
Lastly, I've heard and read many times how amazing it is that Buran landed so close to centerline in such a dramatic crosswind (around 33 knots). I think that would indeed be pretty impressive... if it were true. However, I urge you to go look at video of Buran landing (example, mute recommended). Does that look like a 33 knot crosswind to any pilot? To me, it looks like about a 5-10 knot crosswind at most. You see the wings doing very little correcting, and the wheels touchdown at almost the same time, which is very much not indicative of a crosswind.
For comparison, take a look at STS-133 landing. Note the wing movement at 8:58 which is to correct for about a 12-knot crosswind gust, which looks about right to me. Notice how the upwind wheel hits the runway about a second before the downwind wheel hits - very indicative of a crosswind.
I have no idea where the crosswind number came from, but it was almost certainly exaggerated, either on accident (perhaps mistaking wind conditions on approach for surface wind), or intentionally exaggerated to show how great and superior Buran was. Either seems plausible to me.
I tend to be in the camp that says anything you build which successfully goes to space and comes back safely is pretty exceptional, but I wouldn't say Buran was a tremendous advancement over existing technology, and ultimately it's always going to be difficult to really assess a ship which only flew once.