What return does most angel investors want?

In most cases, what motivates a angel investor to invest? A higher percentage of return a bank could give? If they can get 15% back on money over 3 years, is that the incentive? or does an angel investor want a small percentage of the company too?

Generally, angel investors will make an investment into the equity of the company which, by definition, means that they take a proportion of the company. Angels, in most cases, do not make a debt investment into a venture.

An angel will give the company a "pre-money valuation". They'll then invest money. The "post-money valuation"=pre-money + money invested. The proportion of the company owned by the angel is equal to the money invested divided by the post money valuation.

eg: pre-money valuation of $1M
Money invested $2.
Post money valuation=2M+1M=3M
Proportion of company= 2/3=66%

This means that the angel will be entitled to 66% of the proceeds upon the sale of hte business.

Generally, an angel investor hopes to make about 20% to 30% from their portfolio. However, as these investments are very risky (which is why the financing comes from an angel as opposed to the bank which is much cheaper), and most of the individual investments will lose all their money, the return expected from individual investments is much higher. The 20% to 30% will be an average of high successes and dismal failures.