The opinions of the Luftwaffe pilots varied greatly. What they thought of the P-38 depended upon the circumstances they encountered it under. A German pilot who bounced group of P-38's flown by green pilots over Germany, with numerical superiority, was likely to have a lower opinion of the P-38 than a German pilot who got his bellybutton handed to him by Graham, Morris, Olds, Ilfrey, or Lowell.
The P-38, properly flown and maintained was a match for anything short of a 262 or a 163.
It is true, of course, that SOME German pilots thought the P-38 was an easy mark. It is also true that SOME German pilots would rather sandpaper a tiger's bellybutton in a phone booth than fight a P-38 on even terms.
This argument has been hashed through on these boards ad nauseum. The P-38 was not a dominant plane for the 8th AF. But neither was it an easy mark for the Luftwaffe when flown by a competent pilot.