As requested by several users here, I decided to post this blog in regards to the ME vs DA conversation, adding in my own thoughts. So, here you go!
Mass Effect and Dragon Age. Two RPG series developed by the company BioWare. Each has their own expansive fandom and universe, novels, films, and comic books. Both series have excellent writing and great storytelling, compelling and iconic characters (Shepard and Morrigan), detailed settings, and superb voice acting. They each follow a similar structure in storytelling (ie customizable protagonist leading a bunch of misfits, saving the world/galaxy/whatever, visit key locations to complete your quest, defeat the well-intended extremist and the eldritch abominations that threaten to destroy the world/galaxy, two starting companions are a mage/sentinel and a warrior/soldier, etc. And romance and sex). While both franchises have their own twists and turns, they eventually followed more original plotlines.
However, despite their similarities, both Mass Effect and Dragon Age have numerous differences. For one, Mass Effect is a mostly hard-military science-fiction shooter/action RPG (quite a mouthful here), while Dragon Age is a dark heroic fantasy tactical/action RPG (with DAII empathizing on the action part). In Mass Effect, you play as a single protagonist in a spanning trilogy, Commander Shepard, while in Dragon Age, you play as multiple protagonists throughout the series (the Warden/Warden-Commander in Origins and Awakening, Hawke in II, and the Inquisitor in III. Nobody expects the Inquisition!)
While both franchises gave BioWare much success, Mass Effect, has garnered more recognition, sales, and appeal, receiving higher overall review scores than Dragon Age, though the latter enjoyed its more niche status. As of this writing, Mass Effect has sold approximately 12 million copies on the Xbox 360, PS3, and the PC, five million more than Dragon Age.
As for the gameplay, the original games for both were more akin to traditional Western RPGs, though their sequels became more fluid, more quickly, and streamlined.
Each franchise has its own merits and quirks (I could be here all day on this). However, they're not without their flaws. For starters, there were numerous criticisms against Mass Effect 3's endgame due ot its abruptness, little variety, and percieved plot holes, though much of it is addressed by the Extended Cut DLC. There are also flaws in other games, such as the clumsy control of the Mako on the 360, the texture issues (where it didn't load completely by the time the game's loaded), loading time, and the inventory system in ME1, the slow pacing, and the Orzammar level in Origins, and the copy-and-paste levels (moreso in DAII), along with some...divisive characters in DAII.
Overall, while each franchise has its own ups and downs, but Mass Effect has the advantage with its large audience and recognition. However, these advantages could prove to be fatal when it comes to slipping up from time to time.
Wikipedia (laugh at me, if you want)