" I dont think would have done better than me" and how you can say this statement ? May be he looks or sounded underconfident as per your vision but actually did or doing a better job. Its like what makes you think he was not better thn you. ? Also, its alright if you are not selected and maybe the recruiters made a bad decision but you cant just keep thinking about the same, If required as for the improvement feedback from the HR so that they can share the exact reason for not selecting you. or else just move one and try best in next interviews