Not necessarily. The realized rate of return depends on several factors:
1. The length of time it has been put into a 401K vs the real inflation rate. The longer, the lower the real return. This is especially true in the 2000s.
2. What the 401K is invested in. Whatever it is invested in will determine the actual return, which then still gets eaten away by inflation.
3. Investment losses, which do happen.
4. Any premature withdrawals, which usually have to be paid back with interest.
5. Taxes. Traditional 401K's are taxed as regular income at retirement while only the employer contribution is taxed in a Roth 401K since you contribution is post-taxation.
6. The actual matching by the employer. This can be variable, based on the company, and is optional.
7. Maximum yearly contribution ceilings.
401K's are not a panacea and it must be remembered that this money is effectively tied up until retirement within the financial sector of the economy. Taxes, inflation and risk eat away at the return and most people never consider these aspects, never realizing that the rate of return they think they are getting is higher than what they actually receive.