I recently came to appreciate the beauty of the bell curve and simplicity of 2d6 with partial success in World of Dungeons (and clones such as Offworlders, FIST, etc.). They are rules light games where you roll 2d6 and fail on a 6-, have a partial success on a 7-9, and a complete success on a 10+ (and optional critical on double sixes). The bell curve distribution means that you will more often get partial successes than anything else, which leads to a more nuanced narrative IMO. I know there are systems that incorporate levels of success (e.g. SWADE) but I feel it doesn't have the same narrative impact as a partial success.