I recently played Emerald, so I would like to contribute to this thread.
Firstly, I'm not sure which tier to put it in (maybe mid-high) but Geodude/Graveler/Golem deserve a mention. It is a really nice Poke to have if you choose Torchic, because I did, and I ran through all the gyms with only Blaziken/Graveler/Gardevoir. Even if you don't evolve it, Graveler seriously helps against Wattson and Flannery (Magnitude spam) while resisting their moves, and is also good against Norman to hold off Slaking's Facade.
Other details- You get Geodude early, in the Granite cave. While Brawly's Pokes laugh at it, it single-handedly sweeps the entire Mauville/Lavarigde gym. It also gets decent moves early on like Rock Throw (Lv. 11) and Magnitude (Lv. 16).