Hyperbeem said:
Gyarados is really good in the 5th generation but I disagree on one point. I think it was very effective in the 4th gen when paired with the right Pokemon. It was like the dream come true 6-0 after one turn of set up pokemon. Also, with Intimidate it was great on stall teams too with Rest Talk. I guess it's going to be a great Pokemon even this generation.
Ok let me clarify. Bulky and RestTalk Gyarados both had there places. RestTalk especially was quite good when used correctly as it stopped / countered a lot of threats. Bulky Gyarados worked because it took advantage of its respectable defenses and Intimidate.
Offensive Gyarados was severely overrated. By going completely offensive, you're passing up a lot of Gyarados has going for it (read: unique and good typing / bulky stats). It's also revenged quite easily, like i said. It has to rely on an attack with 80 base power, which in the great scheme of things is not very good. Rotom-A didn't take much damage from Gyarados no matter what moves it used, as it resists Bounce, Waterfall has low base power, and it's immune to EQ. Waterfall does more than Stone Edge too, factoring in STAB. Gyarados' biggest weakness is probably passive damage. By the time you have a DD, chances are you only have 50-60%, which leaves you open to just about any common Scarfer.
Gyarados was also significantly outclassed by Salamence and Kingdra before and then after the Mence ban. If you simply put a Choice Scarf on Salamence, you already have much more Speed and Attack than +1 / +1 Gyarados, without the turn of setting up. Outrage also has the additional 40 base power over Waterfall. Kingdra also does the sweeper role better than Gyarados because of its typing. Since it's only weak to Dragon-Type moves, not much will be OHKOing it, especially since very those Dragons won't be switching in. Kingdra also only needs two moves for full coverage, as opposed to Gyarados' three, which still leave it with holes.
If i'm playing seriously, I can't see myself using any Gyarados that doesn't have significant investment in HP and / or the defenses. Even that Moxie Gyarados I referenced earlier has a good amount of HP IVs. If you're going to use Gyarados, you need to be using it's defensive attributes. Otherwise, chances are you'll be outclassed by something.