There are many Content Generator tools in market today, some are platform agnostic and some are user friendly and creative. Though i list Top 5 with my experience i would recommend to play with all below options and try to create a strategy on what works best for your Content style.
Try to not to focus only on Content idea's also review there strategies for conclusion, Market research, Suggestions on performance and Marketing strategies. That way it helps us in building a content which will stay for long time and will retain readers due to quality contents.
Most of the above tools suggested from the keyword tool listing covers volume analysis, the competition, seasonal trends and negative keywords.