ScouseMouse180: Yeah I quite like the fact that all 3 Dark Souls games have fairly big noticable differences, and all 3 of them are great in different ways. Yeah the bonfire right next to Fume Knight definitely made it a little less painful... they weren't so kind with the run to the Blue Smelter Demon!
I'll have to have a look and see if Demon Souls is available on the Sony store, I've heard people say they think it's the hardest of them all, would you go along with that? Ahh yeah I've been recommended Nioh once I finish with Dark Souls, I wanna give that a go, but Bloodborne is up first
I think Dark Souls 3 could be my favorite overall, as it has the best combat ( due to the addition of charge moves and weapon arts ), it's much more up to date than the old games, and it has a great game world, with lots of little Dark Souls 1 & 2 references. However, I didn't like the characters quite as much in DS2, the soundtrack isn't as memorable as in Demon's Souls and DS1, and I wish they would have kept the bonfire ascetic feature. That's why I find it hard to pick a favorite, because they all have some flaws, but also their own strengths. That said, I love how the final DS3 DLC ties it all together, not just the story of DS3, but the entire series. With that in mind, I feel like it doesn't really matter which game of the series is better or worse, because it all feels like one long, epic adventure.
Anyhow, as for Demon's Souls, I like to think of it as a rough diamond. From Soft had a unique vision, and Demon's Souls is their uncompromising take on that vision. That means it arguably stands out even more, when compared to modern AAA games, but it also doesn't feel as refined as its sequels/spiritual successors. It's actually easier than Dark Souls in some ways, because you can cheese the hell out of most boss fights and many regular opponents. On the other hand, the game is also much more punishing and unforgiving when you screw up. Just to give you an example: In Dark Souls 1 you can ask the pardoner to forgive you for your sins, when you accidentally attack an important NPC. In DS2 and 3 you can even revive them/interact with their grave stones if you killed them. In Demon's Souls? If you kill a blacksmith or important trader, they're gone for good. You just made the game a lot harder on yourself -- Good luck! Also, did you get used to the convenience of bonfires in the Dark Souls games? Demon's Souls doesn't really have those. You only unlock a checkpoint/warp point when you defeat a boss. You can still unlock shortcuts in some areas, but generally you'll have to overcome longer distances to reach the boss of an area again if you die.
If some of that sounds negative, let me add that I still think it's a great game, and absolutely worth playing for anyone who got hooked on this remarkable series. Demon's Souls has the most original ( sometimes weird ) soundtrack of the series, almost every boss fight is unique in some way, and it has some rather iconic characters such as the Maiden in Black, or the first appearance of "Patches". And there's just something about the atmosphere of the game... It's the shortest of the series, too, but that makes it well suited for multiple playthroughs.