Hmmm, lemme see here...
Best Representatives
Generation 1 - Charizard: Let's face it, it has been said many times, but Charizard is definitely the most popular Kanto starter to date, if only by appearances alone. The fact that it was made dominating in the anime series solidified its popularity. It looked like a dragon and can breed with and learn Dragon-type moves. On top of that, it is also one of the Dragons in Pokemon Ranger, even though it isn't Dragon-type, which gives an idea of what Nintendo thinks of Charizard. Finally, it is the only fully evolved started to be made a playable character in a Super Smash Bros. game (Brawl, in this case). Charizard's media attention is without rival among generation 1 Pokemon aside from the obligatory Pikachu, in my opinion.
Generation 2 - Suicune: This was a bit tough, but I ultimately have to go with Suicune. It is the most popular of the three beasts, and was even a mascot of Crystal. It has a bit of media attention in the anime/movies moreso than most other Gen 2 Pokemon. On top of that, it has a really cool sounding cry befitting a legendary Pokemon. I know when I saw it for the first time in-game (I didn't even know it existed, as I never owned any strategy guides, etc.), my jaw dropped in awe, as it was the first roaming legend I encountered, and I thought it looked amazing. Oddly, I mistook it for a unicorn than a dog or cat.
Generation 3 - Swampert: This was very hard, as most Pokemon in this Gen are not very great in standing out in terms of design. I could've been bias and say "Metagross", but to be realistic, I'd think Swampert had a bigger impact than any other Gen 3 Pokemon for its bulk and power. It defined the term, "bulky water" as it only had one weakness that was apparently not as easy to exploit os others. Then you have the fact that its pre-evolution, Mudkip, had its meme "you like Mudkipz?" or something along that line. Sure, there's Salamence and Metagross in their Pseudo-legend glory, and Gardevoir and its "clown car" of Rule 34 references and what-not, but overall, I'd say many people who has played Generation 3 would agree that Swampert may be the best representative of the Advanced Generation.
Generation 4 - Lucario: Sadly, there isn't much in the way of Pokemon that sticks out other than Lucario. It's the only non-legend in Gen 4 to have its own movie and has gained some media attention with merchandise and even becoming a playable character in Super Smash Bros. Brawl. Other than that, there really isn't much else to say about this Pokemon.
I'll go over my list of worst representatives at a later time.