Depends on your goals/needs as a rider. This is not to contradict anything already stated. There are great tires to be had today. Here's my experience so far:
Pirelli Angel GT: On my former K1600 GT. If you want sticky over longevity, these are great. I've run these on different bikes when my primary goal was to few life at an angle. I'm sure they'd be great on a GS. But probably not the right rubber for most use cases.
Dunlop RS4: On my current K1600B: All round tire. Great in the twisties, but can't run that hard with this behemoth of a bike. And great on the open road. Don't know about longevity yet, on my first set. And as mentioned the Big K eats tires. My habit has always been to change them early, when they start to underperform and way before they're completely wasted.
R1250 GS now: TKC 70 up front and Dunlop Trailmax Mission in the back. My first tires on my first GS. Well, the bike did have Bridgestones when I first bought it, but those are Barney Rubble tires. They don't count. The Big K is my all-road bike. And the GS is used on and off-road. These are surprisingly good on the road. I don't scrape my knees in the twisties, but I don't hold back either. All I can say is they're much better off-road tires than I'm a rider. I've run them at full pressure as well as 10-12 psi in a motopark. So far, so good. Why the different tires? The front TMM wasn't in stock at the time, so I chose what I determined to be the best match for my goals. Good decision so far.