I noticed recently that 95% of Genesect are Choice Scarf these days, so I've started using an Expert Belt variant and it's really doing work on stuff. My team looks like Genesect would logically be Scarfed, so it makes it even easier for me to bluff it and catch something severely off-balance with a move they weren't expecting.
However, I don't agree with you that it is suspect material. Many Pokemon threaten it when it's not Scarfed, and the Scarf set has to lock itself into an attack, so it becomes laughably easy to check, especially if you happen to be packing Protect. Heatran and the pink blobs both wall it hard - granted, it has U-Turn, which can make things dicey, but in a 1v1 situation standard Genesect will never win that matchup. For that reason, Choice Band Genesect sounds intruiging right about now - if it wasn't for the sheer volume of bulky waters running around I might give it some more thought. Anyways, my point being that sure, Genesect is strong, but it has its checks and counters, just like all the other strong OU Pokemon. How do you beat Specs Latios without a bulky Steel-type or Tyranitar? Yeah, exactly. There's a reason most teams carry one of those two, and that's because Latios is such a big threat. Same thing for Genesect. We've already seen Heatran usage rise drastically to combat it. It's a top-tier OU Pokemon, no doubt about that, but it's definitely not Excadrill or Thundurus.