He's a goalscorer and was awesome in his pomp, but I would have to seriously doubt his motives for the move. We need someone up front who is proven at Premiership level and who sees a move to us as a move they're willing to work hard to make a success. Someone who may not do something for eighty nine minutes and then pop up and score; we have Crouch and Morientes who try to do all the donkey work (Or in Morientes case failing to in the main) but no striker like above. Fowler has played in a more Beardsley/Litmanenesque role, in contrast with his early days where goalscoring was his primary game. He could still do a job, but he's not the answer to us needed a goalscorer.
Cisse has gained a lot of sympathy of late from Reds to give him a run upfront, and I agree that, with the bit between his teeth Cisse looks a more attractive option than the legthargic Morientes and fading Crouch; but there have been so many times when I've felt like this and Cisse comes on to remind us why he doesn't get near the side.
Ronaldo would be an imrpovement certainly, but there's better, hungrier (and not just with pies other wise there'd be no one hungrier than Ronaldo!) strikers around for next season.