It can be pretty hard to compute the right number. What you need to know for your actual return is called the dollar-weighted return. This is the Internal Rate of Return (IRR) http://en.wikipedia.org/wiki/Internal_rate_of_return computed for your actual cash flows. So if you add $100 per month or whatever, that has to be factored in. If you have a separate account then hopefully your investment manager is computing this. If you just have mutual funds at a brokerage or fund company, computing it may be a bunch of manual labor, unless the brokerage does it for you.
A site like Morningstar will show a couple of return numbers on say an S&P500 index fund. The first is "time weighted" and is just the raw return if you invested all money at time A and took it all out at time B. They also show "investor return" which is the average dollar-weighted return for everyone who invested in the fund; so if people sold the fund during a market crash, that would lower the investor return. This investor return shows actual returns for the average person, which makes it more relevant in one way (these were returns people actually received) but less relevant in another (the return is often lower because people are on average doing dumb stuff, such as selling at market bottoms).
You could compare yourself to the time-weighted return to see how you did vs. if you'd bought and held with a big lump sum. And you can compare yourself to the investor return to see how you did vs. actual irrational people.
.02, it isn't clear that either comparison matters so much; after all, the idea is to make adequate returns to meet your goals with minimum risk of not meeting your goals. You can't spend "beating the market" (or "matching the market" or anything else benchmarked to the market) in retirement, you can only spend cash.
So beating a terrible market return won't make you feel better, and beating a great market return isn't necessary. I think it's bad that many investment books and advisors frame things in terms of a market benchmark. (Market benchmarks have their uses, such as exposing index-hugging active managers that aren't earning their fees, but to me it's easy to get mixed up and think the market benchmark is "the point" - I feel "the point" is to achieve your financial goals.)
