A policyholder bought a 25 year participating endowment from AIA. She asked for my view. 

I looked at the benefit illustration and gave this reply.
The important point to consider is shown here:

EXTRACT FROM BENEFIT ILLUSTRATION
Based on the Illustrated Investment Rate of Return of 4.75% p.a., your total Illustrated Yield at
maturity is 2.38% p.a.

Based on the Illustrated Investment Rate of Return of 3.25% p.a., your total Illustrated Yield at
maturity is 1.50% p.a.

These returns are not guaranteed and do not represent the upper and lower limits of the returns you
may receive.

Please note that the guaranteed maturity benefit of your policy may be less than the total premiums paid.
You can compare 2.38% and 1.50% Illustrated Yields at maturity with the returns of Singapore
Savings Bonds and Singapore Government Securities. You may refer to http://www.sgs.gov.sg/
savingsbonds.aspx and http://www.sgs.gov.sg/ for more information on the returns of Singapore
Savings Bonds and Singapore Government Securities. Please note that the Illustrated Yields at
maturity have taken into account the cost of insurance and expenses incurred.
END OF EXTRACT

You are investing  your money for 25 years and will only get a return of between 1.5% to 2.38% per annum. 
This is extremely low. 

You should not compare this return with Singapore Savings Bond and Singapore Government Securities. You should look at other investment choices, e.g. 

Temasek Bonds 2.7% for 5 years. 
Straits Times Index ETF (used to be 9% p.a. over 20 years, but has probably dropped to  8% p.a. now).
CPF special account - 4% p.a. plus bonus

This policy gives you a poor return because of the high distribution cost, effect of deduction and the profit margin of the insurance company.

If you are looking for life insurance cover, buy a term insurance.