John's answer addresses cranial capacity well, but the question is about intelligence. The idea that brain size maps significantly to intelligence has been thoroughly debunked since the era of phrenology. Scientific American notes that "brain size accounts for between 9 and 16 percent of the overall variability in general intelligence" in humans, and digging into the studies shows that this measure of brain volume has stronger correlations with potential pathological factors than it does to innate volume-- many forms of brain trauma or developmental issues incidentally also reduce the volume of brain matter, but two healthy individuals with similar backgrounds but different brain volumes have even less difference in measured intelligence. In other words, I'll make better guesses about my friends' IQ if I know their childhood nutrition and adult drinking patterns than if I know their hat size. I should also keep such speculations to myself if I want to continue calling them "friends".
These studies are also using only human participants, for obvious reasons. The same article discusses how structural differences allow other species to have highly developed cognition in particular realms regardless of their brain size. This is to say that brains which develop differently will think differently. So depending on the origin of your elves, I'd expect them to do badly on human IQ tests, but humans to also do badly on theirs. Again, social factors have an enormous impact on efforts to quantify the huge messy collection of traits we loosely clump together as "intelligence", and that's within the same species. CJ Cherry's "Foreigner" books are all about how apparently human-like aliens have fundamentally alien cognition, and the traps that come from attempting to map their abilities and motivations onto a simple spectrum defined by human perspective.
Of course, this all assumes we're landing on the material side of the Cartesian duality debate. Tolkien's elves (and humans as well) explicitly have a non-physical self, the "fëa", which exists independently of their body. If gods are tethering thinking and feeling souls to ambulatory meat, then all bets are off in terms of brain size and intelligence. Perhaps the brain in that case merely functions as the interface between the meat and the astral self, and merely needs to be large enough to send and receive signals.
TL;DR: No, big eyes don't mean less intelligent-- and also that's probably not the right question to ask about how a different species thinks, and why.
