EXCELLENCE OF TAWHEED

1. The primary purpose of our creation is to worship Allah alone i.e. Tawheed.
Allah says: "And I (Allah) created not the Jinn and humans except they should worship Me (Alone)."  [Qur’an: Adh-Dhariyat (51): 56]

2. Allah commanded us to single Him out in worship before other commandments. 
Allah says: "Worship Allah and join none with Him in worship, and do good to parents, kinsfolk, orphans, Al-Masâkin (the poor), the neighbour who is near of kin,..." [Qur’an: Nisa (4): 36]

3. Allah sent Messengers to every nation inviting people to solely worship Him and avoid directing any form of worship to other than Him.
 Allah says: "And verily, We have sent among every Ummah (nation) a Messenger (proclaiming): 'Worship Allah (Alone), and avoid (or keep away from) Taghut (all false deities).' …"  [Qur’an: Nahl (16): 36]
Allah further says: “And We did not send any Messenger before you (O Muhammad SAW) but We inspired him (saying): None has the right to be worshipped but I (Allâh), so worship Me (Alone and none else)."  
[Qur’an: Anbiya (21): 25]

So, the first obligation that we are commanded with is Tawheed- Singling out Allah in worship. This is what Laa ilaaha illa-Allah refers to. We should emphasize more on Tawheed than any other good deed because no good deed is acceptable unless it is based on pure Tawheed.
Being Muslims our first call should be towards Tawheed because of its excellence and great importance.