Ideally, I want a pick in the top 3. But I'd settle for a top 5 as well.
And IMO, I think we should forget this whole "number of top5 picks in previous championship teams" or whatever. I think the more obvious point is, multiple all stars on a team stand the best chance at winning a ring. A way of acquiring an all star (on the cheap too!) is by drafting him.
Now, it's true that drafting an all star and keeping an all star are two different things. So let's say a team like the Bucks drafted one and he's available because Milwaukee is a lost cause. The next question to ask is, how well can the C's attract FA all stars? Exactly. Thus, it stands to reason that we probably stand a better chance at retaining our drafted all star rather than attracting one another team drafted via FA.
Trades are a whole other issue, but I would assume that a pick in the top 5 is worth more than a pick in 10-15. The better asset would, in theory, make it easier to trade for an all-star.
That said, while top 5 picks aren't surefire all stars, the odds of you getting one while picking in that range are much higher than if you pick one in the 10-15 or 10-20 range.
We're not doomed if we don't get a top 5 pick. I mean, never say never, right? But it's not a farfetched thing to think that the road to prominence would likely be harder and longer if we didn't. We'd also likely need more luck as well, and "luck" or "chance" seems to be what "anti-tankers" are allergic to the most.