For most people life insurance is not the best way to save for retirement, either because of the risk or because the guaranteed return is low.
Term policies don't include a cash value or investment component, so they aren't relevant to this question. Permanent policies, however, accrue a cash value over time and include an investment component, which is why they're occasionally marketed as retirement savings products.
Of the types of permanent policy--whole, universal, variable, and variable universal--only whole guarantees a cash value, but the rate of return is conservative. The other types aren't guaranteed and can lose cash value over time.