It's hard to say what ROMs are "better." There are so many to choose from on the OV, it all really boils down to: what do you prefer? I use a stock Froyo ROM because it is simple, stable, and good on battery. CM7 ROMs have many more features and some are actively updated, like Mirage. CM9 builds have ICS features.
But here's the link to the official IHO CM7 BACKside ROM, the first one. You can download it to your SD card and flash it in recovery if you want a truly CLEAN install:
http://forums.androidcentral.com/op...inferior-human-organs-unofficial-cm7-1-a.html
Alternately you could simply enter your custom recovery and wipe the cache and dalvik partitions. Doing this, regularly, can make the phone less sluggish.
If you want the phone to get back to a clean state, without installing a ROM, you can do a data wipe WITHIN the recovery, but you will lose all your apps and data - unless you have a backup on your SD like Titanium.
Finally, you could also try something simple, like downloading SDMaid from the Play store. This will helo clean your SD card and uninstall all those apps that you accumulated over time, but don't use anymore. That will also help your phone's performance speed up a bit.
Facebook
Twitter
Instagram