completely agree - the power of the overall market is undeniable (as we could witness the last two day).
Concerning the Hard Cap itself there are a few factors to take into consideration:
1) As the Hard Cap allows the estimation of the total mcap of a project, it is important to know how much of the total % of tokens the investor is to pay for (let's assume the Hard Cap for 50% ist 15Mil - then the total mcap would be at 30mil) - then it is advisable to compare to projects in the same space and their respective mcap, which allows the estimation of whether or not the demanded sum makes sense (Note here: sometimes tokens are locked away and often not included in the Hard Cap!)
2) It depends on the size of the project - for instance if an entire new blockchain is to be created, then I'd view anything below 35Mil (by now, as trend is clearly pointing towards higher caps...) as appropriate (e.g. take a look at Neuro) - with a plain app this sum would obviously be too high.
Of course there are other factors that also apply to ICOs in general: Teamexperience - Size of the team - Stage of the product (MVP; Alpha; Beta) - Partners - Competition , but describing all of them would blow this thread out of proportion.
Note: This only reflects my personal opinion and experience and is not meant to be taken as a guide or general rule of thumb that promises succes. In fact, feel free to disagree. As everyone should, I always love getting to know a different perspective and learning a thing or two.
Hope everything makes sense. Kind regards