They're all great guitarists, but there can be only one.. i choose Rudolph because he has been with them through hell and high water, he's an absolute maniac on stage even though he's 60, has written some of their best stuff, and generally seems to keep the band going, Klaus may be the "face" of the band but Rudolph is the engine. not to disregard the other guitarists, technically they may be far better than Rudy(especially Uli) but he wins as an overall guitarist and musician for me.

I like moust albums whit Michael Schenker(why he left band? )
early day albums sp I vote for him

Well the combination of Micheal and Rudolf must have been something special in the early 70s. Jabs certainly dose not degrace himself though he is also an outstanding guitarist.
The best in relation to the Scorpions I would have to say is Rudolf Schenker, for two reason, he is still with the scorpions and has been since the beginning, he writes some of rock musics most catchy riffs... like 'Rock You Like a Hurricane', 'Edge of Time', 'In Trance', 'Blackout' and this is just the beginning of a very long list spanning 35 years or more.