1. Actually they are. Both have overworlds with portals to other worlds where you must complete various objectives to earn star-esque relics. Both have Red and Blue Coins. Both have no Luigi. Both have a boss that you face repeatedly throughout the game. Both have secret Sub-courses. Both have similar controls and moves. Both have a total of 120 star-esque relics. Both have Yoshi. Both have a stage populated by Boos. Both have characters that you can speak to. Both have giant/king/boss versions of classic Mario enemies. Both have guys that you can race against(more than once). The only differences are that SMS has FLUDD and no ice level and Yoshi isn't playable in SM64.
2. About what?
3. Prove it.
1.Lots of Mario games have red and blue coins, portals and what you said there. Also,I don't think we can really count Yoshi sleeping on the roof actually featuring in SM64
2.About it being the sequel, obviously. What do you expect? A few years ater it's release for them to turn round and say "Oh, we forgot to mention that Sunshine is Super Mario 64's sequel"? I think not!
3.Prove it. How sad and babyish is that. You can't get more pathetic, or ignorant for that matter. "Just because it came after it, it doesn't mean it's the sequel" is not a thing you can prove. Ok, I say that Super Mario Galaxy is... erm... Super Mario World's sequel. And Double Dash is Super Mario bros. And Luigi's mansion is Yoshi's Island's sequel. Do you really agree with tha? If not, grow up!