I have completed Gears of War and have about 4 hours on Resistance.
I do agree that the Gears of War graphics are better. Resistance graphics look a little washed out and dull, but don't get me wrong they are still amazing for a first gen title. Both games were viewed in 720p.
Resistance, so far, has a much better story and does not use annoying voice acting. Too bad the majority of the story cut scenes are pictures instead of full motion video though. Also, Resistance went away from the "big buff stupid tough guy" army characters which is great.
As far as online play, Resistance is better. Most of the time, the more people the better and Gears does not give you this option. But, please keep in mind that Gears and Resistance are two very different games. Gears is a "duck and cover" game and Resistance is more of a "run and gun" game. So both games are very fun online and do work, it's just I am more of a "run and gun" type of guy.
Resistance controls are great. The game makes use of ALL the buttons a lot of the time. The environments are very interactive and feel real. Gears of War also does a great job with the controls and the environments. Resistance's world just feels bigger.
I think that Resistance, in general, is under rated and under hyped. The game was over shadowed by Gears, and the PS3 in general, was over shadowed by the Wii. Rating scores for Resistance were around a 9 and scores for Gears were around a 9.6 out of 10. This was Xbox 360's very first major exclusive release after a year, which helped the game receive better scores, and people jumped all over it.
Don't get me wrong both games are AMAZING!