That doesnt even make sense. Kevin Johnson was on the Suns long before Barkley was traded to Phoenix. And to say the Kevin Johnson was better in his twilight years (after Barkley was traded, 96-99) than Nash is pretty stupid. You could say that he was better than Nash in his prime, but that was before Barkley.
So saying Nash is the best Sun since Charles Barkley is saying Nash is better than the likes of Kidd, Marbury, Marion etc. which is a pretty reasonable claim considering the MVPs, playoff wins etc.
Your timeline is all jacked up because you dont have a clue what you are talking about.