I only played Ninja Gaiden 1 and 2 (I think) and it was very linear, but Souls games aren't. The path you take is pretty much up to you in many areas, some will be more challenging than others depending on your level and equipment.
For example, on my first play through of Dark Souls I got to the Tomb of the Giants (grrr) and got right to the end of the area and realised I could not go any further without a particular item. Same when I failed to be able to access The Abyss because I'd not fought a specific boss fight and picked up an item from it. The game doesn't lead you, you're expected to figure it all out for yourself e.g. which path to take and which bosses to fight and when. Rarely do you get any help from NPCs. This is part of the challenge and it's so refreshing once you get used to the shock of not having your hand held or fed everything.
