As of today, one would most likely use Opus, which outperforms most other codecs, as can be seen in the following chart (from Wikipedia):
Opus works across the entire bandwidth (from narrowband to fullband), and always provides better quality than even dedicated speech codecs, due to its ability to switch encoding mode dynamically depending on the bitrate and bandwidth.
My old answer from 2013 is below.
According to a few studies I've read, G.711 seems to provide the best tradeoff between required bandwidth, compression delay and subjective audio quality.
Cisco published an article in 2006, Understanding Codecs: Complexity, Hardware Support, MOS, and Negotiation, where they also evaluated the subjective Mean Opinion Score (MOS) over a couple of codecs, which mostly include those you mention. MOS range from 1–5, with 5 being the best quality, as averaged over a number of listeners (usually more than 12–15).
The results were as follows:
+---------------------+------------------+------------+-------------------------+
| Compression Method | Bit Rate (kbps) | MOS Score | Compression Delay (ms) |
+---------------------+------------------+------------+-------------------------+
| G.711 PCM | 64 | 4.1 | 0.75 |
| G.726 ADPCM | 32 | 3.85 | 1 |
| G.728 LD-CELP | 16 | 3.61 | 3 to 5 |
| G.729 CS-ACELP | 8 | 3.92 | 10 |
| G.729 x 2 Encodings | 8 | 3.27 | 10 |
| G.729 x 3 Encodings | 8 | 2.68 | 10 |
| G.729a CS-ACELP | 8 | 3.7 | 10 |
| G.723.1 MP-MLQ | 6.3 | 3.9 | 30 |
| G.723.1 ACELP | 5.3 | 3.65 | 30 |
+---------------------+------------------+------------+-------------------------+
As you can see, G.711 still requires more bandwidth than the other codecs, which were developed for ultra-low bandwidth applications, but in your case, with ADSL, this is no issue. What you get is a very low delay with good MOS values.
A more recent 2009 study by Karapantazis et al gives an even better overview (click to enlarge):
As you can see, there are certain broadband codecs which you could also take into account, Speex being very popular.
