My first "adventure" tourer was a 78 Kawasaki KZ750B2 (twin). I was doing a lot of riding in the deserts of Northern Mexico and the high country of eastern California. The bike came to me from a guy nicknamed "Crash" and looked as if it had been dragged for days under a bus. It had fiberglass bags which I promptly removed (not paying attention and rode into an arroyo tearing both bags off). I replaced them with a set of 37mm ammo cans bolted to a set of homemade mounts (superb bags, waterproof, huge, indestructable if a bit heavy). The tires were, more or less bald (at 18 you don't really know very much) so I replaced them with full knobbies as I was off-road as much as on. This bike took me everywhere my VF750 would not and I had a blast doing it. Was it a great adv. tourer? Absolutely! My second foray was an 81 cx500 Honda (reused the same 37mm cans after the KZ was destroyed by a nearly blind (but awfully nice) old guy who ran it into a building while parked.The bags had one small dent...Verdict on the cx? Excellent! This was the most overbuilt bike in history. Liquid cooled, shaft drive, all for a 500cc twin. The bike was everything you'd want for rough overland touring (might've had more ground clearance). It was eventually replaced by a gs80 which was, of course, even better. It was the places I went, not really the bikes that made these years of riding so very good. I had thought I was very intrepid until I came across a guy on a 74 fl way up a set of fire roads in the back of beyond. No mods, street tires, just patient competent riding. Just shows that you can go anywhere if you've the will to.
Just playing Devil's advocate for a moment... have you ever noticed that the more difficult (arduous, nightmarish...) the trip, the more we remember? If you want a real adventure, take the worst imaginable bike for the job. Say, like Emilio Scotto, a Gold Wing through jungles, or perhaps a Hayabusa through Baja (no pavement, either) a 75 CZ Falta replica with lights cross country on interstates. If adversity breeds character, these trips would be very character-building. But they wouldn't be dull!