According to Reuters, Nintendo's market capitalization is now 6.30 trillion yen (approximately US $51.1 billion), vesus Sony's 6.64 trillion yen ($53.8 billion). Though Sony shares have increased 72 percent over the last two years, Nintendo shares have reportedly shot up four-fold in the same period; it's that same increase that has made former Nintendo CEO Hiroshi Yamauchi now the third wealthiest in Japan.
Sony obviously still has sizable market value over Nintendo and current success is not indicative of long-term staying power (e.g. Nintendo's pre-PlayStation dominance), but the House of Mario has certainly found (and capitalized on) a large market. Nintendo, Sony Defense Forces: don't shoot the messenger.
Sony PlayStation 2 1st-gen
Sony PlayStation 3 (late 2012)
Sony PlayStation Portable PSP-2000
Nintendo Wii console