At the end of the day, I think Parsons will fall under the Luis Scola, Kyle Lowry, Kevin Martin caliber type of player. Players that are considered by many to be a "borderline all-star(s)" or aka amazing role players.
Too offensively effective to be a Battier-type, IMO and as others have pointed out. He seems especially good at the complementary role in offense, taking advantage of situations where the defense overdefends the main offensive guys. Battier had mixed results in that role for us. Also, Battier's top quality is his team defense and team play in general. Parsons is a great one-on-one defender, but I don't think he's a standout team defender. The closest we got to a Battier-type team defender last season was Patterson, I think. I'd be more than happy if Parsons could play that role for us.
Parsons is not an almost star. He may currently rank among the top 10 small forwards in the NBA. In that sense he will never be a star. However Parsons is elite in 'bro-ness'. He seems to have enough charisma that you can build a team around him. With him and McHale in the locker room can you ever imagine that team chemistry would be a problem? I cannot. Can Parsons turn the tide in recruiting battles for young stars? It has been documented. Can you imagine a situation that Parsons cannot diffuse among the young core of the Rockets? Well I can, but it would be incredibly unlikely to happen. I think Parsons has better judgement than that. So realistically Parsons already is an elite NBA player. His worth is determined by more than his abilities on the court. The Rockets are very lucky to have him.