Journey collector's edition. Includes Flow and Flower. They are all pretty easy, and if you like beautiful relaxing games with really nice soothing music, they're a must have. There really isn't anything to collect though
Okami HD. Another beautiful game, I consider it one of the best games ever made. Plenty of stuff to collect.
The Fallout games are really good and pretty cheap. Huge open worlds, tons of stuff to collect. I prefer New Vegas, but you really can't go wrong with Fallout 3. Replay value is really good.
Skyrim/Oblivion - Same as Fallout but in a fantasy setting rather then post apocalyptic
Sorry if I'm necroposting something, but I don't care.
I would say Dark Souls is easier, if for no other reason than the poise system. In Demon's Souls, pretty much anything will stagger you. In Dark Souls, hits have to break through poise to stagger you. Thus, melee is at least easier due to poise in Dark Souls.
Demon's has easier healing items though (in that they can be farmed/stockpiled) and a mana system as opposed to a casting number system, though, which can make mages much stronger.
If you like 2D platformers at all, Rayman Origins is probably the best 2D platformer of this generation (the other possible contender is Super Meat Boy) and is one of the best of all time as far as I'm concerned.
The mechanics themselves are pretty simple and there's collectibles and w/e, and it's gorgeous and a total blast, especially with friends for the local co-op. It does get quite difficult at times (get hit = die, and some levels are pretty hard not to get hit in :P) but adding friends helps mitigate this immensely (you don't lose until everyone is dead, and living teammates can revive dead ones) and each "room" of a level has its own checkpoint so it's not like you have to replay the whole level to get past the hard parts.