It's purely imaginary, but it's a feeling that can only really spring from playing the original game. A quick summation doesn't quite do it.

Beyond that, there are the simple feelings of familiarity engendered by playing the original game. After taking down Sovereign, I felt like I had gone to war with Liara, Garrus, and all the others, and I was delighted to see them all again in Mass Effect 2. My character's romance with Liara in the first game was a little silly, but it made me exponentially more interested in the Shadowbroker DLC and other Liara-centric story threads.

It's true that by skipping out on the first game, you skip the muddled shooting mechanics and the painfully slow opening. But you also skip out on being able to move seamlessly from an alien planet to the Normandy (something sorely missed in Mass Effect 2), and being able to force Saren to shoot himself in the head. Likewise, skipping out on Babylon 5's first season means skipping "Infection," but it also means skipping the introduction of The Great Machine, the Babylon 4 mystery, and Morden's first, brilliant introduction.

As with many long-running series, even a flawed first chapter can have its merits if you're a dedicated fan.