OP - you arguably ride one of the longest lived bikes ever built.
I'd have to say over 4 decades of riding that Honda would take top honours....both from an owner and observer status tho upfront costs seem high. My 305 Honda Hawk I regretted selling to get a 250 Yamaha. The Hawk was much more durable.
My son's Honda 230 motocross bike was a stronger machine than the Yamaha he got tho the Yammie 250 was much higher stressed motor. The 450 Honda motocross he ended with was well built and reliable for such a highly stressed machine.
Of the three trial bikes the Honda TL125 was most reliable over the Yamaha and Bultaco - hell wish I had a TL now to do forest hikes on
That said the Suzuki Burgman 650s I've owned have been zero problems at all - not a single issue in 50k of riding over two machines in 2 years.
One guy took his 42,000 km continuous around Australia also without a single issue and there is one rider with 140,000 miles on his.
First gen of these had some issued but like many models have matured over the years. That complicates your quest.
From a model standpoint the Kawi KLR650s sure have stood the test of time. A 20 year run 1988 to 2008 with only minor changes and reliable enough for the US Marines.
My advice....stick with the Honda marque if you can afford it.
For value for reliability in a middle weight tourer - the Burgman 650 is hard to beat.
Best all around machine I've ever owned and many other owners concur.
http://www.burgmanusa.com/forums/
It's relatively low stress motor combined with a magic transmission seems the ticket.
I notice Honda and BMW are moving into the midrange with automatic category with DCT from Honda which is also offered on the VFR1200 DCT and now moving into the smaller machines.
That new Honda 700 motor with incredible mileage looks to be a winner.
Depends a lot on what you are looking for. Reliability in a midrange bike I think may be harder to achieve as they generally work harder and of course the owner has some play in this.
Some machines may be super reliable if the owner pays close attention.....others can go with minimal supervision.