Agreed, Bullock was no longer a big draw at that point in her career (Miss Congeniality 2 four years easier proved this). So it was the combination of the two of them that created a monster hit. And Sandra hit the jackpot a few months later, solidifying her name as A-list Oscar winner.
Ryan on the other hand had nothing of quality lined up, so he's still in the same place as he was before The Proposal. A somewhat famous actor that can't be linked to a genre and neither he or Hollywood has a clue what to do with his career. The fact that he starred in one of the most notoriously awful films of recent memory isn't helping him much either.