Your list does not use the complete designation.
Current AMD graphics cards are called Radeon Ra bcc(X).
a designates the general card level and can be 5, 7 or 9
b designates the card generation (until now we have 2 and 3)
cc differentiates between various cards within the same generation and general level (higher number should mean greater performance)
X - optional (only present on some cards); designates a slightly better version (for instance R9 380X is better than R9 380, but not as good as R9 390).
R5 bcc - entry level, for users that just want a card that outputs video, also for HTPC and similar usage; not for gaming.
R7 bcc - mid-range cards that can be used with acceptable results (acceptable at least for some people) for gaming;
R9 bcc and now also R9 Fury - high end and "enthusiast" level cards.
For Nvidia:
GeForce GT abb or GeForce GTX abb(Ti)
GT class of cards is more or less the equivalent of R5 class from AMD (not for gaming).
GTX - cards (more or less) usable for gaming; covers the performance range of cards that AMD covers with two classes of cards (R7 and R9), so it not as indicative of the performance level as the R7 and R9 designation used by AMD are.
a - designates the card generation (we have 2, 4, 5, 6, 7, 9 - the way that Nvidia counts)
bb - designates the card performance class (higher number means better card).
bb = 50 (Ti) or 60 (Ti) - mid range cards, good for gaming
bb= 70 (Ti) or 80 (Ti) and Titan cards - high-end and "enthusiast" level cards
Ti suffix, if present, designates a better version of that card (similar with X suffix on AMD cards). For instance GTX 750 Ti is slightly better than GTX 750, but not as good as GTX 760.
This is the general idea/in theory.
What you can not tell from this labeling schemes used by AMD and Nvidia is which are really cards from a new generation and which are just re-brands/re-labeled cards.
On mobile GPUs (used on laptops) the situation is even more confusing because of re-labeling and inconsistencies.