Well some of that is true, Xanthine but i kill the steel pokemon before it can even touch me LOL.
That still doesn't mean Water > Steel. (Or, for that matter, Water > Grass.) Water does neutral damage to Steel and vice versa, so if you're not overleveled or better trained, it's actually still an even match. Likewise with Grass-types. If you're on an even level, you'll still end up with a problem and will want a backup Pokémon. (For example, if you go up against Erika with a level 45 Feraligatr, you'll want a couple of backups just in case because there's no way to be certain you'll be able to take her out before she takes you out.)
Well grass i also kill since waterpokemon (well some of em) can use ice attacks, and grass is weak against that.
In that case, your argument is that Ice > Grass, not that Water > Grass. You can teach the same Ice move to a Normal-type and still get the job done --
without the defensive weakness.
It's great that your strategy is an all-out offense, but there's a bit more to strategy than that. Yes, you can overlevel like crazy and get by on offenses, but if you want to be cautious and want a full team, you can't just rely on one Pokémon because you never know if that one Pokémon will be wiped out. For example, if you get that Pokémon Toxiced, you've got two options. First, you can heal up, which means you leave yourself vulnerable to the Pokémon you're facing. Second, you can ignore it and keep going with the hope that you'll be able to finish off your opponent before they finish you, but you run at a risk of letting the poison run its course.
Actually, a better example of this would probably be Morty. He's early enough in the game that it's
before you can get proper TMs or levels to get your Totodile to actually be a formidable fighter in comparison to the GLs, even if you choose to rely on a single Pokémon. His Ghost-types are neutral to Water-type attacks and vice versa, but before you'll land a hit, he'll try one of two things: Hypnosis or Curse. If he lands Hypnosis, he'll Dream Eat the crap out of you, at which point, you're still screwed because Water is neutral to Psychic as well. If he lands Curse (which will probably be more likely), you're screwed because there's no way to heal Curse, and it works quickly. Either way, this happens with the first two Pokémon he sends out. He's got four in total, and at the levels you're at when you reach him, you're relying on luck to take him out first unless you overlevel. (At which point, the entire argument of whether or not Water's the best type is moot because
anyone can beat a type matchup if they overlevel.) So, if it's Gastly who uses Curse, you're facing down Gengar with a huge chunk of your HP gone, even if you're able to wipe out Gastly right after. Alternatively, if it's Haunter, you're still facing down Gengar, whose main strategy is Hypnosis + Dream Eater either way and who will most likely take your first hit and/or outspeed you (because, let's face it, Gengar's got better stats than a Croconaw -- which you probably will have by then -- in the specials department).
Point is, Water's got its weaknesses, and just because it's neutral doesn't necessarily mean Water has the advantage. I love Water-types myself, but I realize that I can't rely on
just it and that a Water-type isn't always the best type for the job. (For another example, Piplup got me screwed against Lucian because neutral hits against Bronzong meant it could Psychic the crap out of my Empoleon, even though we were at an even level, and I had Surf.)
