Here we have a classic RPG hack'n'slash'nexplore formula that hits the pleasure zone again and again. Simple in that everything is laid out in a farily striaghtforawrd way. Unlike Realms of Arkania, the RPG system is fairly straightforward. Where things get complex is in how advancing levels and finding treasure are done in a myriad of ways. There are so many tough, unique dungeons with different monsters, you're pretty much staring down at least 100 hours of game. 4,5 and 6 alone could be desert island experiences.
I also love how your adventuring party evolves and you grow incredibly attached to them through their epic journey. There's enough of a plot and direction so you never feel totally lost, but there's also enough freedom so that you really do feel like you're just on this massive and epic romp!
These games have style to burn, as well, with great, hand-drawn art-direction.
You can tell the people who made these games poured their souls into the them. Masterpieces, one and all.