Unfortunately, Lockyer suffers more than a few handicaps in this race.
First and foremost, he was forced to shift from Fullback to Five-Eighth. He was the best fullback in the world, and he also made the best Five-Eighth in the world, at least for a little while. However, his best work at 5/8 is still nothing compared to what he could do at Fullback, so he suffers by comparison.
Secondly, he is playing on in the twilight of his career, with his form fading as a result. Johns went out when he still had a bit more to give, and so he is remembered more fondly than Lockyer, who we can point to on the television and say "I remember when he used to be much better than this."
As a player, I would say that Lockyer was better than Johns. He was able to transition from Fullback to 5/8, displaying greater versatility than Johns. He was also able to subsume his ego and play for the team, something johns never had to do; the Knights, New South Wales, and Australian teams he played with were built around playing to his strengths and nothing else. When you are the focal point for your team, it is much easier to be noticed.