Splinter Cell definitely wins the Stealth and Actions part. MGS is more popular mostly because of the strength of the characters, even though the stories aren't great.

Metal gear solid

Hmm, metal gear solid is a lot better story wise.

This

Splinter Cell wins in the stealth area. As for the story I think Splinter Cell has a more realistic story but Metal Gears story is more memorable. Either way I don't really keep up with either one.

Since when does realistic story mean better story? Ever heard of star wars, lord of the rings,...?

I think the Splinter Cell stories have atleast more coherence, which is important for a story. In the MGS games there are simply too many moments and holes that put you in disbelief and takes away part of the immersion.

I prefer SC because of the fantastic gameplay (at least in 1 & 3, that is) and the downright badassness of the game.

MGS has its plusses, though. Even though I think Kojima is a story hack, the amount of polish and work put into the games is truly phenomenal.

Overall, they're both fun games for very different reasons. SC is a better straight-up stealth game while MGS has its share of fun quirks and pretty amazing game moments.

Characters - Metal Gear
Story - Metal Gear
Stealth Gameplay - Splinter Cell [Pure stealth]
Overall Gameplay - Metal Gear [More options]
Graphics - Metal Gear
Lasting Appeal - Metal Gear

Despite the stealth essence, they're both very different game.

In fact, I wouldn't even compare them but since you're asking, MGS beats the crap out of Splinter Cell.

I would call the graphics a tie because up until recently the Splinter Cell games had better graphics. This finally changed with MGS4.