Shivji is called 'Bhola' (innocent, kind hearted, easily pleased) because it is believed that He is easily pleased and grants boons instantly (hence he is called Ashutosh). Krishna, in comparison is a difficult God to please. You see Krishna is not interested in rituals. He wants total surrender and Love. So it depends upon what you consider easy or difficult.

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http://www.dalsabzi.com/Language_Festivals/shivratri.htm