They got me again when I found the MSV Estevanico.
In truth, Mass Effect has had its hooks in me since the first time I stood in front of the Citadel Council and dobbed in that crazy old bastard Saren. Back then, as I struggled to assimilate the quirks of the stupid inventory system and put up with a cover mechanic apparently thrown together on someone's lunchbreak, the scale and disposition of the universe was suddenly sold to me in seconds. With the fates of billions of lives at stake, I was told, I would need something a bit more convincing than, er, dozens of eyewitness accounts of Saren killing a fellow Spectre and ransacking Eden Prime in search of Prothean leftovers in order to get him into trouble. Disbelief: suspended.
So while everyone else sobered up at the beginning of 2010, I tore into a slightly buggy review copy of Mass Effect 2. (Don't worry - I played the whole way through a retail copy to double-check my conclusions. Twice.) At the time, I was amazed how far BioWare had gone to overpower criticisms of the first game - by scrapping my beloved Mako, streamlining all the major systems and breathing action into static conversations - but it wasn't until I first diverted myself away from the main story quest that I really fell in love again.
The MSV Estevanico disappeared without a trace roughly a year before the events of Mass Effect 2, only for Commander Shepard and his intergalactic recruitment roadshow to discover its epic bulk teetering over a cliff edge, crash-landed on the planet of Zanethu (Ploitari system, Hourglass Nebula - but I'm sure you knew that). And in a game where I spent most of the time ducking, diving and slinging magical homing fireballs around in-between firing sniper rounds, I found myself climbing over the gigantic corpse of the Estevanico, listening to the ghostly sighs of its creaking bones and looking for an explanation.
I flew away and landed on Canalus (Pylos Nebula, Dirada system - obviously), where I could barely see my hand in front of my face, let alone enemies popping up in the middle distance (or Miranda standing next to me - cruel and wonderful Miranda). So I tiptoed around in the fog fighting off Geth and looking for weather beacons. I think I saw a dragon. Anyway, I found some meteorological survey team corpses or something and left again.
By this stage I had completely forgotten what I was meant to be doing. I was exploring. Alone among the dozens of RPGs I've played and loved over the years, Mass Effect 2 really made me want to explore, rather than simply giving me the option to do so, and it did it really cleverly - first it encouraged me to mine unsurveyed planets using the scanner device, and then sometimes it located an anomaly, which meant it was time for an away mission, and unlike the bouncy, homogenous wilds of Mass Effect 1's epic fringes, each new destination planet had character and a story to tell.