What a coincidence, you can!
https://www.techspot.com/review/379-crysis-2-performance/page8.html
This is before the Sandy Bridge days, so there isn't a more recent i3 in the mix. But you can see the i5-750 being insignificantly faster than a Nehalem/Westmere-based i3.
https://www.techspot.com/review/467-skyrim-performance/page7.html
Here you can see the Sandy Bridge i3 outperforming the i5-750.
https://www.techspot.com/review/458-battlefield-3-performance/page7.html
Again, Sandy Bridge i3 and i5-750 performing exactly the same.
Since then, the i5-750 has been removed from the benchmarks. But since we've seen about 20~25% improvement in IPC between Sandy Bridge and Haswell, as well as a sight clock bump between the 2120 and the 4130, it's not hard to imagine what it would look like today. Also, you can go back to any performance test in the last few years and still see i3 processors consistently beating Phenom II X4 models (still in the benchmarks), which is the other "quad-core" recommendation made by this game.
Also, the i5-750 is not overclockable (just like the i3). The "K" models already existed back then, you'd need a much more expensive i7-870K to overclock.
The Civilization review, while a fair example of i5s being significantly faster than i3s back then, it from the Nehalem/Westmere days. It's an entirely different thing to compare a Nehalem i5 to a Haswell i3.
And you must be having some trouble comprehending the "i3 vs i5 vs i7" article. In it, when using the GTX 980, the only games where the difference between an i3 and an i5 is significant is in Metro Redux (about 18%), and arguably in Thief (about 11%). It's <10% in every other case, and again: with the GTX 980. For a CPU that costs just 53% of the price of the i5 (i3-4130 vs. i5-4690), so even with the GTX 980 the i3 is still much better value. Keep in mind that on both Metro Redux and Thief the i3 still stays above 60 FPS.
Now, with the GTX 960, that difference disappears completely. The worst case is again Metro Redux, and the i3 provides a bit over 93% of the performance for about 53% of the price. This is the
worst case for the i3.
Finally, the article makes it very clear that there are no tangible benefits in getting an i7 for gaming. Best case scenario is 8% higher performance than the i5 in Metro Redux. I don't know where you got that idea from.
Objectively wrong.
Someone buying an i3 in 2015 gets a much better value than any quad-core CPU and mostly insignificant reductions in performance, as show in the comparison article. That same article also shows that an i5 provides almost no benefit for a "decent" GPU like the GTX 960/R9 285, and for high-end GPUs (you didn't mean to imply only high-end GPUs are "decent", did you?) like the GTX 980 or R9 290X an i5 can bring benefits, but an i3 can run it perfectly well too, so an i5 is certainly not a "must have".
Of course, if you have the money, then by all means, get the i5. But the whole point is that saying things like "this game requires a quad-core", "the i3 falls behind pretty much in such games", "having an i5 is a must" and "poeple who don't buy quad-cores are *****s" are objectively and demonstrably wrong statements.