Have there been many pokemon a like games since the GBA?
GBA, and GB/GBC saw loads of them; medabots, robopon, various dragon quest monsters games with jokers probably being the foremost, metal walker, arguably demi kids dark version at least, monster rancher maybe (though the PS1 version remains my favourite, wonder how many people have audio CDs to do things with today), telefang, jade cocoon. Most of which for me were better than pokemon.
Since then few half hearted digimon games (not that any would be pokemon clones have particularly lived up to the promise) and boring nonense like Yo-kai Watch... oh dear.
To answer the question about DS games specifically. You might consider Spectrobes if you are going to say Fossil Fighters is like it.