Yep, Sonic should be on the list.  One of the main reasons why I went with the Genesis during the 16 bit era.  The SNES wasn't released yet and I had "a lot" (for a kid) of insurance money from a basement flood that "took out" the Atari 2600 (it later dried and continued to work).  They gave us about 20 or 30 for the system and 5 dollars for each game (had probably at least 20-30 games).  I was eyeing the TG-16 but was convinced to get the Genesis due to Sonic being a bad ass.  My parents actually helped me choose better systems a few times when I was young.  Convinced me to get Genesis over TG-16 and to avoid the Jaguar (for some reason I thought it was bad ass system when it first came out).

Man, some of those games didn't change or influence shit. Some of them didn't even make a ripple in the grand scheme of things.

Decent list but a 40 in 40 list should include one game per year for each of the last forty years.

The Path and Passage certainly prove it. I've never even heard of those games

If it were me, I'd toss in:

Angry Birds: The free game that took the world by storm and showed that mobile games could compete with other games just by being creative

Counterstrike or Call of Duty: Insanely addictive online FPS experiences that border on obssession

Geometry Wars: Showed that there was a mass market for downloadable titles on consoles

Super Mario Kart: created an entire genre almost single handedly (GTFO, Rad Racer/Rock N Roll Racing fans. This was different!)

Wii Sports: Ushered in the motion control craze that was hinted at with the Power Pad, Power Glove, and Activator

If not Call of Duty, then Quake III for giving us console owners an online FPS (as well as console vs. PC play) on the Sega Dreamcast

Guitar Hero/Dance Dance Revolution: the foundation of the rhythm games. Not the first but the ones that sucked in non gaming audiences

Everything that is PC is basically missing, like strategy RTS and MMO.

I'm very sad about the lack of Metroid, but Cave Story's presence makes up for it by far.

E.T. makes total sense to me. Even though it didn't cause the gaming industry crash of the 80s it was blamed for it. The game was so bad it scared consumers off gaming for a few years. It wasn't until Nintendo released the NES that gaming was taken seriously by retailers. E.T. is a very bad game, but it's an important bad game.

Me neither. But I bet they are artsy games.

Yeah. The top actually 10 started well with all being really iconic, hugely influental games and then all of a sudden Ico popped up.