I went to Morningstar's "Performance" page for FUSEX (Fideltiy's S&P 500 index fund) and used the "compare" tool to compare it with FOSFX and FWWFX, as well as FEMKX (Fidelity Emerging Markets fund). According to the data there, FOSFX outperformed FUSEX in 2012, FEMKX outperformed FUSED in 2010, and FWWFX outperformed FUSEX in both 2010 and 2012. When looking at 10- and 15-year trailing returns, both FEMKX and FWWFX outperformed FUSEX.
What does this mean? It means it matters what time period you're looking at. US stocks have been on an almost unbroken increase since early 2009. It's not surprising that if you look at recent returns, international markets will not stack up well. If you go back further, though, you can find periods where international funds outperformed the US; and even within recent years, there have been individual years where international funds won.
As for correlation, I guess it depends what you mean by "low". According to this calculator, for instance, FOSFX and FUSEX had a correlation of about 0.84 over the last 15 years. That may seem high, but it's still lower than, say, the 0.91 correlation between FUSEX and FSLCX (Fideltiy Small Cap). It's difficult to find truly low correlations among equity funds, since the interconnectedness of the global economy means that bull and bear markets tend to spread from one country to another. To get lower correlations you need to look at different asset classes (e.g., bonds).
So the answer is basically that some of the funds you were already looking at may be the ones you were looking for. The trick is that no category will outperform any other over all periods. That's exactly what volatility means --- it means the same category that overperforms in some periods will underperform in others. If international funds always outperformed, no one would ever buy US funds. Ultimately, if you're trying to decide on investments for yourself, you need to take all this information into account and combine it with your own personal preferences, risk tolerance, etc.
Anecdotally, I recently did some simulation-based analyses of Vanguard funds using data from the past 15 years. Over this period, Vanguard's emerging markets fund (VEIEX) comes out far ahead of US funds, and is also the least-correlated with the S&P 500. But, again, this analysis is based only on a particular slice of time.