I wrote Golem as a mid-tier poke, and I do think it belongs there-- but there is no way that Slash and +20 SPE alone make Sanslash better than it.
edit: Rather, maybe this means Golem should be moved to High-tier?
I agree with the premise that Geodude should be ranked above Sandshrew, but I think both belong in the Mid Tier. Here's why:
1) Both require serious TM support. Geodude learns STAB attacks, but unfortunately Rock Throw is very unreliable and Earthquake comes relatively late (i.e. it needs Dig to maximize its potential). Obviously Sandshrew is even worse as it needs TMs for both of its STAB attacks.
2) In the role of a Ground type, Diglett outclasses both of them due to its superior Speed. I've previously said that Diglett is a borderline High/Top Tier, because late game it'll die against most things he can't OHKO (due to his poor Def/Spc), but these two are clearly a tier below.
3) Speaking of late game, both are shaky against the E4. Geodude is slightly worse here, because he struggles against Agatha's status effects (due to his crappy Speed) and is vulnerable to Bruno.
I realize this is a 180 from my initial post advocating for Sandshrew in the Top Tier, but things are vastly different when you're not using X-Acc + Fissure and get penalized for hogging TMs. I think both of these Pokemon have high ceilings (Slash/STAB Dig, STAB Dig/Rock Slide), but overall I'd put them at the top of the Mid Tier.
On a related note: I'd like to agree with atsync and others in moving Growlithe to the Mid Tier. Fire type is already poor in-game, and Growlithe isn't even a good Fire STAB since it doesn't get a good Fire move until Blaine (keeping it unevolved until it learns Flamethrower is completely counterproductive). Yeah, it's got a high ceiling if it gets Dig and perhaps Body Slam, but that draws very similar comparisons to Geodude and Sandshrew, doesn't it?