Historically, the market's average rate of return has been about 8%. (Serakfalcon's "6% to 10%" is essentially the same number.) You should be able to get into that range for long-term investments with minimal risk.
"5 or 6 companies", unless you know a heck of a lot about those companies, is fairly high risk. If any one of those runs into trouble, a considerable amount of your net investment is riding on it. Of course if any of them invents the Next Big Thing you could hit it big; that's the tradeoff.
Diversification isn't sexy, but it buffers you from single-company disasters, and if you diversify across kinds of investment that buffers you from single-sector disasters. Index funds aren't sexy, but they're a low-cost way to diversify, especially if you go with a mix of funds in different categories (large cap, small cap, bond, international, real estate) or a fund which has that mix built into it such as a target date fund.