It’s hard to argue that the top 4 is Storm, Sent, Cable and Magnus, simply because they own almost everybody else for free and they can do decently against each other. Beyond that, it differs a little, but you can reasonably put Strider, Spiral and Cyke in top tier. Cyke’s only real weakness is Cable, otherwise he’s a great assist who holds his own against top tiers. Strider and Spiral aren’t as good as they used to be, but they still own almost anybody below them, and when used skilfully can take down top tiers as well. Note that you do not “play Strider” as a standalone character, you play Strider/Sent/Doom; similarly, you don’t play Spiral, you play Spiral/Cable/Sent.
Second tier has only four real shoo-ins: Commando, Doom, BH and IM. Commando is an assist, yes, but wins tournaments anyway, so he earns his spot. Same with standalone Doom. BH and IM obviously aren’t as good at what they do as the big 4, but have a reasonable chance of survival and some tricks that put them ahead of the amorphous “Everybody Else”. I don’t really consider Cammy and Psy second tier, as in 90% of situations where you’re using them, you could be using Cyke or Commando better.