I always thought Riker was weird for not going to captain the USS Melbourne. I feel like the show was trying to make us understand his position...and I just never could. I always thought it was a little selfish for him to hog the First Officer position on the best ship in the fleet. He had the experience to captain his own ship and he should have been out there mentoring his own crew but to me he played it safe on the Enterprise letting his career pass him by.
To me there was just something weak about Riker. He did great against the Borg...and then nothing of much note after that. He had the 2nd best job in the entire federation and it was just wasted on a guy with no ambition. How many other officers in the Federation wanted to be the 1st officer under Picard on the best ship in the fleet to advance their career...like all of them? But lazy Riker never leaves the position.
Simple, he wanted the Enterprise but only with Picard being promoted and moving on. He gladly gave it back to him after he was restored from being Locutus despite his field promotion to Captain