I voted G2a. But here is my ranking of likelihood :
1) G2a
2) I2a1 (old I2a)
3) E1b1b
4) T
5) J2
6) I2c
7) J1
8) R1a
9) R1b1* or R1b1c
10) I2*
11) I* or IJ
12) F
13) L
I think it is impossible that Ötzi was R1b1b2. R1b is possible though, but only older subclades like R1b1 (P25) or R1b1c (V88), or conceivably even R1b1b*. I cannot imagine how he could be N1c1 or Q either.
I'll give a ranking a shot. I think that you importantly missed I2a2 and I2b and give too little credit to F:
1) G2a -- an obviously dominant Neolithic haplogroup
2) I2a1 (old I2a) -- another obviously dominant Neolithic haplogroup, especially in the West
3) I2c -- didn't apparently spread as fast as I2a1, but spread earlier than most Haplogroup I, and has a center of diversity close to Ötzi
4) F -- already seen in a Neolithic sample, could be a sign of things to come
5) I2a2 (old I2b) -- a later spread than I2a1 and probably a bit farther from Ötzi than I2c, but both are still within range
6) E1b -- still a big question mark, but Ötzi could possibly be our E1b breakthrough
7) J2 -- could be Neolithic, also raises questions
8) T -- ditto E1b, J2
9) J1 -- ditto E1b, J2, T
10) I2b-ADR -- probably too rare and poorly assimilated with farmers, but has a center of diversity not too far Southeast of Ötzi
11) R1b L11- -- could have feasibly spread into Europe before R1b L11+
12) R1a -- we're stretching R1a's range here, but I think it could have spread outside of Corded Ware early
13) R1b L11+ -- this would pretty much mean that Taranis, Maciamo, and I are wrong about R1b L11+, which, sure, is possible
14) I2* -- we'd have to theorize him to be an extinct branch of I2 for him to be I2*, which is now an empty set, although if he is an extinct branch of something, this may be most likely
15) I1 -- I1 clearly expanded far North of Ötzi after he lived, so he would pretty much have to be an extinct branch of it
16) I* or IJ -- another extinct branch possibility, probably too early for Ötzi
17) L -- we're very far outside of L's range, but it could represent early movement of it
18) Q -- ditto L
19) N1c1 -- ditto Q