In plain words
Worshippers of the devas go to the devas; worshippers of the ancestors go to the ancestors; worshippers of spirits go to them; those who worship Me come to Me.
Word for word
Those vowed to the devas go to the devas; those vowed to the ancestors go to the ancestors; the worshippers of spirits go to the spirits; those who worship Me go to Me.
The commentators
Bhagavadgītābhāṣyam
येऽपि अन्यदेवताभक्तिमत्त्वेन अविधिपूर्वकं यजन्ते, तेषामपि यागफलं अवश्यंभावि । कथम् ? —
यान्ति गच्छन्ति देवव्रताः देवेषु व्रतं नियमो भक्तिश्च येषां ते देवव्रताः देवान् यान्ति । पितॄन् अग्निष्वात्तादीन् यान्ति पितृव्रताः श्राद्धादिक्रियापराः पितृभक्ताः । भूतानि विनायकमातृगणचतुर्भगिन्यादीनि यान्ति भूतेज्याः भूतानां पूजकाः । यान्ति मद्याजिनः मद्यजनशीलाः वैष्णवाः मामेव यान्ति । समाने अपि आयासे मामेव न भजन्ते अज्ञानात् , तेन ते अल्पफलभाजः भवन्ति इत्यर्थः ॥ २५ ॥
In plain words
Even those who worship out of devotion to some other deity, sacrificing without following the proper way — even for them, some fruit of that sacrifice is bound to come. How does that work? Let's see.
They go wherever their vow points them. Those whose devotion, whose discipline, is fixed on the gods reach the gods — that's simply what 'devoted to the gods' means. Those devoted to the ancestors — intent on the śrāddha rites and the rest — reach the ancestors, the Agniṣvāttas and their kin. Those who worship the spirit-hosts — Vināyaka, the Mother-goddesses, the Four Sisters — reach those spirit-beings. And those whose settled practice is to worship Me, the true Vaiṣṇavas, reach Me, and Me alone. Here's the sad part: the effort is exactly the same in every case — and still, most of them don't turn to Me, simply out of ignorance. And because of that ignorance, what they get back is only ever a lesser fruit.
Close to the Sanskrit
Even those who, by virtue of having devotion to another deity, sacrifice not in accordance with the [proper] injunction — for them too, the fruit of sacrifice is bound to occur. How [does this happen]? —
They go, [that is,] proceed — devavratāḥ [means] those in whom vow, [that is,] discipline and devotion, toward the gods [is present] — those whose [devotion is] such are devavratāḥ; they go to the gods. They go to the ancestors, [that is,] to those beginning with the Agniṣvātta [class]; pitṛvratāḥ [means] those intent upon rites beginning with the śrāddha, [that is,] devoted to the ancestors. They go to spirit-beings, [that is,] to those beginning with Vināyaka, the Mother-hosts, and the Four Sisters; bhūtejyāḥ [means] worshippers of spirit-beings. Madyājinaḥ [means] those whose habitual practice is sacrificing to Me, [that is,] Vaiṣṇavas — they go to Me alone. [But,] even though the effort is equal, they do not resort to Me alone, because of ignorance; on account of that, they become sharers of limited fruit — such is the meaning.