I'll can't wait until the current generation of historians passes by, and we have a new one that isn't so emotionally tied to Johnson. By any resonable standard, Johnson's was a failed presidency.
His foreign policy was a mess. Vietnam the most obvious (where he escallated a small scale war even though his advisors told him it could not be won.) He did nothing to reign in the Soviets. Ike laid the ground work for combatting the Soviets, but Johnson didn't follow through. It took Nixon to establish a set of treaties to limit Soviet advances (especially in weapons.)
Johnson's domestic policy is loved by liberals, but it was basicly throwing money at the problems. Johnson's domestic programs have ended up being bloated programs that don't effectivly accomplish what they were set out to do.