There are tons of good hacks on Vizzed. I'll detail some of them for you.

Pokemon Fire Red Omega- hack of fire red with same story in Kanto except with all Pokemon up to Gen III available. Also has an increased difficulty, and some Pokemon receive stat and evolution changes.

Pokemon Emerald 386- similar to Omega in regards of having all 386 Pokemon and increased Pokemon, except this time in Hoenn. No Pokemon receive moveset or stat changes, but evolution methods are altered.

Pokemon Flora Sky- a fantastic hack set in an all new region where different Pokemon from all five generations live. Features an awesome storyline and good graphics. Evolution changes.

Pokemon Light Platinum- another new region, Zhery, also houses varying Pokemon from each region. Slightly more difficult than Flora Sky, but features entry if free items/Pokemon and lots of post game. No evolution changes, but all the trade evolution Pokemon are traded to you at some point or another.

Pokemon Prism- Gen 2 hack of Gold that makes the player start with Larvitar in an all new region. I'm pretty sure it's incomplete, but a great hack nonetheless. Notable for having Hoenn Pokemon in a Johto game.

There are many others, but these are some of the best. There is also the Ruby Destiny series, whic you should check out yourself.

The best one fr me so far has been Pokemon Psychic although the extra grass doesn't work, you start out with Legendary Psychic Pokemon like MewTwo and Deoxys(Fail) but you can collect just about all the Pokemon that showed up in the Pokemon games when that one was out. Oh and in the town next to the one you start in you can get free Master Balls, Up to 99 of them and you can go back for more later if you need them.

Thanks guy but I tried Psychic I enjoyed it but not really. Recommend more

Yeah have you tried the Ruby Destiny Series (Life of Guardians, Reign of Legends, and Rescue Rangers)? They're all extremely well put together hacks. I also heard Light Platinum and Liquid Crystal were both good.