Rentals are much more risky, as the housing crash demonstrated. If you really want to benefit from that market, buy a REIT unless you actually enjoy the work of being a landlord.
The gains are here now, and I'm more concerned about a bubble personally. Vanguard's total stock market fund has year-to-date growth of ~17%, and their more-stable lower-growth "balanced" fund with bonds included has year-to-date growth of ~8.75%. Both of those are better than the usual estimate of 7% annual growth for retirement funds (a conservative 3% for inflation and 4% for income).
The gains are here now, and I'm more concerned about a bubble personally. Vanguard's total stock market fund has year-to-date growth of ~17%, and their more-stable lower-growth "balanced" fund with bonds included has year-to-date growth of ~8.75%. Both of those are better than the usual estimate of 7% annual growth for retirement funds (a conservative 3% for inflation and 4% for income).