Wasn't he also offered command of the Drake before taking the posting as First Officer of the Enterprise? The man just seemed unwilling to sit in the big chair! Who gets offered command four times before accepting one??
Yes, he was offered the Drake
before it went to Paul Rice. It's not clear why Riker declined the chance to have a ship of his own. Had TNG ended sooner, it's possible he would have been promoted before any movies were produced. I remember there being talk about his being promoted before Insurrection
, as well. He finally accepted promotion because Starfleet told him that he wouldn't get another offer if he turned the Titan
As Nemesis was the last TNG film, it didn't make sense to keep him on the Enterprise with so many other characters departing: it would have been interesting had Picard sacrficed himself instead of Data, which would have elevated Riker to captain of the Enterprise
, the post he wanted all along.