MD5 is a hash function, not an encryption function. It yields a fixed-size output (128 bits) regardless of the input size. It is not meant to be reversible. Thus, it can not be compared with AES: what MD5 does, AES cannot do, and what AES does, MD5 cannot do.
One situation where you can meaningfully compare processing speeds of MD5 and AES is in protocols where the same data is both encrypted (e.g. with AES) and covered by a Message Authentication Code such as HMAC, which is based upon a hash function (possibly MD5). One such protocol is SSL/TLS. In that case, we can try to see which of the encryption and the MAC uses most of the CPU budget. Usually, encryption is more expensive than hashing, which the numbers you give show. Note, though, that MD5 is known to have a number of weaknesses. The standard hash function which is believed to be "as strong" as AES is SHA-256, and SHA-256 processing speed is not much better than that of AES, on commonly used CPU.
Another situation is a PRNG. You can build a PRNG out of a block cipher (such as AES) by encrypting successive values of a counter (this is called CTR mode). You can also build a PRNG out of a hash function by HMAC-ing successive values of a counter. In that case, this works, for the hash function, on its output bandwidth, not its input bandwidth, and it requires hashing many very small messages instead of one big message. Usual hash functions, including MD5, turn out to be disappointingly slow when used that way.
This explains why we define block ciphers such as the AES, instead of using a one-size-fits-all hash function everywhere.