nice sig!
anyway, using Gravity means you'll have a lot of better abusers than Terra. for one, you can feel free to spam Ground/Dragon coverage as it now hits everymon for neutral. Fast special sweepers can now afford to run the more pow/less acc moves such as Starmie, which makes them a real thread. And spikes support is virtually mandatory, as is (obviously) gravity.
What i'm trying to say here, I guess, is that Gravity isn't a field effect you can just throw on one mon like TR is. If you want to use it successfully, you really have to have a team built fully around it, and in that case, you've got better options than Terry.