Bad - SeuSeu, Vaeliki, Kevin McGuiness come immediately to mind although there are plenty more, especially directly before and after the Northern Eagles.
Good - Kennedy is the best, both Stewarts, Bryant, Hicks, Donald, Lyon, Robertson, Monaghan, Matai, Williamson, Kite, Bell, Hasler, Ballin, Cochrane, Rodney, Gillespie, Innes all come to mind and there are many many more
Also think it's harsh criticising Ben Walker, he was an excellent buy for the Northern Eagles (279 points scored in 2001) and he had injury problems after he came back to Manly (I seem to recall him getting concussed a few times). Andrew Walker was great in 2004, and I remember cursing when he got sacked, we could've really used him in 2005.