I'm thinking it has more to do with the rest of the lineup, but here's an analysis anyway of how often Reyes took an extra base or scored on a sac fly.  It actually favors Reyes more than the people who knock him in, in that a slower player might not have taken the extra base.  

The Goods

Reyes had taken a lot of extra bases (by which I mean going from 1st to 3rd on a single, 1st to home on a double, 1st to home on a single, or 2nd to home on a single) - He's done the above 10 times, and scored each time - the only time he went from 1st to 3rd, he ended up scoring on a fielder's choice.  

That's 10 times out of 31 times on base, which is remarkable.  Unsustainable, but remarkable nonetheless.  

By my count, this is out of only 11 chances - he has only stopped at 2nd on a single once.  He has not yet scored from first on a single.

When he scored from 2nd on a single, 4 times, it was because he singled then stole second.  Another time, he stole 2nd, took 3rd on the throwing error, and scored on the next hit, a single.

He has moved over by sacrifice (bunt or fly) 6 times.  This has resulted in 4 runs.

So of the 18 times he scored, 10 were at least partially because he took an extra base.  2 were from scoring on sac flies, 2 from a sacrifice to move him over to 3rd and a single, one from a double play, one from taking 3rd after a throwing error on his steal attempt and a subsequent single, and only 2 by the home run (one from himself, one from Delgado)

He has stolen 10 bases, been caught 2 times, and picked off once.  If you don't count the pickoff as a CS, that's 83.3% SB/CS, and if you do, it's about 76%.  

This is interesting stuff - while Reyes obviously needs a higher OBP, he has in fact made the most of his times on base.  The people behind him have had hits, but Reyes has taken the extra base on nearly ALL of those hits.

This analysis seems really ludicrous to me, but from what I tell from the box scores and play by plays, it's accurate.

It's still true though, that Reyes isn't a good leadoff hitter.  When he gets on, he scores more often, and it would seem, creates more than other players, but he still makes too many outs (I think), which then offsets his abilities when on base from a statistical standpoint.

But if the above is real ability, and not just small sample size, he's a better baserunner than I had thought, and if he can increase his contact, keep up the walk rate, and make fewer outs, then I can easily see him being one of the best leadoff hitters in the game (if you believe in leadoff hitters, of course).