I'd take the following over him for sure:
In the same ballpark (meaning arguable who gets picked over whom):
Reyes (arguable, but 2b is so weak)
I think people over-value young studs in keeper leagues. In keeper leagues, your time horizon is either this year or next year. Forget about 3-4 years down the line. Too much can happen. Plus, there are always good young guys who come into the league that you can get.
5 years ago you might have built a fantasy squad around Bonds. You'd have gotten 4 years of fantastic production (01-04). And then nada. And Manny is the riskiest in that sense. But four years is a long time. You would most certainly have been competitive if not tops in the league. Trading can happen at any time too. If you have Pujols, you should be able to get antother top keeper PLUS another keeper or player that will help push you over the top for a stretch run. So Pujols is the runaway choice at #1 for me.
About 5 years ago, I built my roto keeper (15) around Manny (must have been about 29-30 at that time and has been solid - slightly younger than Ortiz today), Berkman (young), Halladay (later traded right at his peak in the off-season after his Cy), Crawford (his rookie year, so I got him cheap), and Helton. Helton is tapering off, but i am still glad he was my first round pick at that time. He gave me 2-3 years of top poduction and he still contributes. If I could pick only one top keeper, it would be Manny or Crawford and I'd have a hard time deciding. Both are great and I wouldn't hesitate with either.