So... I used the search button and couldn't find the answer (unless my search terms sucked, if so please forgive me).
I come from a Street Fighter background, I understand frame advantage and have a basic understanding of the options my opponent has in frames. I can't seem to translate Street Fighter frame understanding to the Smash 4 frame understanding. There feels to be a lot of factors involved when attacking and defending.
In reference to frames,
How do I figure out if a move is "good" or not? (For example, In street fighter a 3 frame normal attack is usually considered good.)
How do I figure out if a move is "safe on shield" or not? ( In Street Fighter, when the opponent blocks and you attack, if you're minus frames on block, your opponent has a chance to either punish you or push a button)
Traditional understanding of frames simply is not that helpful in this game...in fact it's likely more crippling than anything because you expect certain things to happen intuitively, and they don't. Some easy rules of thumb to make it easier:
1) Unless you are playing Little Mac, there is simply no blockstun in this game. It does not matter how powerful you are, or how much startup your move had.
2) This also counts for blockpush. There is none if you aren't Little Mac.
3) If it got blocked, and you're in grab range, you are unsafe. In fact, you're probably being thrown right now.
4) Aerials too. This is why most people who use them fadeaway as they throw them out, to avoid being in punish range in case they're blocked. If you can't do this, it's just always unsafe on block.
5) Grabbing the ledge gives about 1 (maybe 2) frames of vulnerability.
The only real frame data that really matters in Smash 4 is Startup and Active. Startup to know how fast it is, Active to know if it'll catch rolls, dodges and ledge recoveries. That's about it. The main thing to worry about in smash 4 is hitbox size and range. You notice i didn't say Recovery, and that's mostly because it can be played by eye, and is only important if the attack wiffs. If it strikes then it's good, if its blocked, its unsafe.
There are a few really good moves that are safe on block, but this is only because they have long reach and low landing lag. Moves like Link's Nair, ZSS' Zair, ect. They are completely unsafe on block at close range.