In Heart Gold you can only get an Ekans in the game corner(maybe in some later PokeWalker stages as well), but they are common in SS.
Man I've spent 73 hours already, and my pokedex count is... 73:lol This is gonna take forever, and I haven't even beaten Morty of Ecruteak City yet.
Actually I did have a go at him earlier this morning, but got my ass handed by his lvl 25 Gengar. My problem is that eventhough I've spent over 70 hours already, I haven't concentrated on just a 6 man team, but everytime I get a new cool pokemon I just can't put it in a box and never use it. I did the same thing with Pokemon Red, and ended up having lots of lvl70+ pokemons at the end.
Current team:
Bayleef (24) | Quagsire (22) | Metang (22) | Murkrow (22) | Magby (21) | Elekid (21)
And then as backup(or just pokemans that I care about
)
+At least 10 others above level 20