Bodkin: Well, they're using different tools to catch players attention. I see them both like subgenres to the old (dungeon-like) kind of FPS - Doom, Blood, ect.
And about sandbox shooters, it's not that bad. Stalkers, Far Cry 2, Boiling point, Xenus, precursors and just cause/gta if you don't mind merge them with TPS.
It's ok, i just need to say something about that :)
Technically FPS is already a subgenre. But yeah, open world FPS are a different breed, that's for sure.
Far Cry 2 was almost universally good - if it wasn't for the fact that the game constantly rained generic shoot-on-sight enemies down upon you. I still completed it and I liked the ending. But I can't think about that game without remembering the constant torrent of enemies pouring out of everywhere. I must have killed half the populace by myself.
Ultimately Far Cry 2 serves to highlight exactly what I was talking about when it comes to poor substitution for scripted action.
Boiling Point's flaws are the stuff of legend. The change logs are comedy gold. White Gold is pretty good overall. Some polish and a proper translation and it would be a very, very good game indeed.
Precursors has the same shortcomings, is a bit more polished but doesn't seem to have much of an ending to say the least. If those two were properly fixed up and finished then I'd actually buy them again for sure. But as it stands they just highlight the other problem common in open world FPS - unfinished buggy games.