When a co headline tour between Maroon 5 and Train was announced a few months back, screams were heard from preteen girls bedrooms across the nation. And for those in New England, the big night finally came August 13th at the Comcast Center. It seemed as though the crowd was split evenly between diehard “Trainettes” and screaming “Marooners”. Gavin Degraw was scheduled to open but had to miss the show after being beaten in NYC the week earlier.   The crowd was shocked when the curtain dropped for the first time and it was Maroon 5 on stage, rather than Train, who was expected to open. Adam Levine and co played a 14 song set filled with versatility. The energetic dance track “Moves Like Jagger” started things off and from there they group moved seamlessly from hard rock tracks to delicate ballads and even jazzy crooning tracks. “Sunday Morning”, the 3rd track in, showcased Levine’s voice and was definitely a crowd pleaser with it’s laid back riff and it’s infectious chorus. The set flowed very well and there was barely any time between songs. It seemed like a every song that was played was a smash top 40 hit, because it was. Only after hearing a set do you truly realize how relevant Maroon 5 has been in pop music over the last decade.    The band struck gold with the crowd by playing “Makes Me Wonder” and “Misery”. The two smash hits drew ear splitting screams throughout their duration. The next great song of the night was “This Love”, which concluded the main set with an anthem like quality that left the crowd screaming every word. A rare first act encore saw the veteran crew bust out their best song of the night, the new smash “Hands All Over”, which got the crowd going with a hip hop-like beat and a shredding guitar part courtesy of James Valentine. After a strong finale with the power ballad “She Will Be Loved”, it seemed almost surreal that the show was only half over.    And that’s why they should have headlined. Train seemed like an after thought when they took the stage. While they do have some smash hits to their name, their live show hasn’t developed enough to headline such a large venue. Pat Monahan has a voice to match Adam Levine’s but his stage presence leaves much to be desired compared to the more experienced Maroon 5 frontman. That’s not to say there weren’t some good tracks. “Calling All The Angels” and “She’s on Fire” both drew big responses from the crowd, as did “Hey, Soul Sister”. “Parachute”, the opening track was unusually flat and “Ordinary” wasn’t much better. Many outfit changes and overly jaded stage antics (such as running all around the ampitheatre during “Marry Me”) also took away from the set.    Together, the show was good. The order should have been reversed, and that would have taken it to the next level as a fantastic pop show. As I left, it kind of let me yearning for what could have been. Maroon 5 was fantastic, and Train would have been as well if they had only opened.