I'm going to not call out your explanation as trolling and instead try to use logic in this.
While yes, it may seem like Smash is just a big case of advertisement, there are plenty of other factors that contribute to characters as well, namely popularity or what potential Sakurai sees in them.
First, your point on Pichu and Roy.
As unbelievable as this may be, they weren't in solely for advertisement purposes (well, maybe Roy was), nor because they were new and relevant (or going to be in Roy's case).
Pichu especially. Clones were afterthought characters when Sakurai deemed the roster too little (wouldn't you if there were only 8 new characters?) Pichu was added as Pikachu's clone as it added more of a flair than Raichu for being a joke character in hurting himself.
Roy, I admit, had advertisment on the mind, as he was trying to give a preview of a character that was going to debut later. However, he also stated that he added Roy to "advertise Fire Emblem as a whole". What he meant by that is anyone's guess.
Now, moving on to Lucario and Ike.
Ike had nothing to do with advertisment. Sakurai wanted to have a new Fire Emblem character, but didn't know who to include, so he went to Intelligent Systems for a suggestion. They suggested Ike.
Lucario had much more than advertisement going for him; he was also very popular of a potential new character and was viable (viability is the main reason why someone like Deoxys was turned down and why a 2nd Gen was a mere afterthought character in Melee).
Snake and Sonic were not included to advertise recent or upcoming titles.
Snake was included because Kojima wanted Snake in the game for the sake of his son, who wanted to see one of his father's characters in Smash.
http://www.joystiq.com/2012/03/19/thank-kojimas-son-for-getting-snake-into-smash-bros-brawl/
It also goes to note that Kojima tried to get Snake in Melee, at which point this was far prior to Twin Snakes.
Sonic was the last character to be added to the roster (but not the last one to be finished; that title presumably goes to Wolf) due to the sheer amount of fan demand he had, far exceeding that of any other candidate, be it Nintendo or 3rd Party.
His inclusion had everything to do with fan support and nothing to do with advertising the Mario and Sonic Olympics (though that may have contributed to the fan support).
Now, to Mega Man. You claim that Capcom would pick someone else rather than him for the sake of money, but this is incorrect.
Capcom has stated before that they are perfectly acceptable with Mega Man being in Smash, though it is up to Sakurai as it is
his game.
http://megaman4smashbros.wordpress.com/2011/07/01/extra-ask-capcom-july-1-2011/
Also, even Street Fighter's main developer would rather see Mega Man than one of his own characters; but if it HAD to be limited to a Street Fighter character, he'd rather have M. Bison than Ryu.
http://www.qj.net/wii/interviews/yo...characters-hed-like-to-see-in-smash-bros.html
Like before, he said that it is ultimately up to Sakurai whether or not a Capcom character even makes it.
Hopefully this has been insightful.