If you play 300 games in the NHL, that's a good career. Means you've stuck around on merit for probably a couple full seasons or at least been useful for several seasons. That's a good Draft pick. In the 15 drafts from 2000-14, 28.6 per cent of Draft picks from mid 2nd-round (47th OA) to the end of the second round played 300-plus NHL games. It's dispersed randomly, no clearly better results the earlier the player is selected in that range. The big drop-off in expected NHL success starts in the bottom quarter/third of the first round.
Why 300 GP? There's a fairly significant difference between the number of guys who play 300 and those who play just 100 (38 per cent of draftees in the latter half of the second round from 2000-14). It eliminates those who accumulated 100 at least partly because their team sucked and they fit in somewhere, usually over a number of seasons with different bad teams, despite not being a good player themselves.
Also, about 300 GP is where player pension benefits really become meaningful, about $80K per year if you wait till you're 62., less if you start collecting at 45yo.